Opinion by Judge GOODWIN; Partial Dissent by Judge REINHARDT.
GOODWIN, Circuit Judge:Joshua William Sanders appeals his conviction and sentence on two counts of mailing a threatening communication. 18 U.S.C. § 876. He argues that the district court erred: (1) in concluding that his offense did not constitute a “single instance evidencing little or no deliberation,” U.S.S.G. § 2A6.1(b)(2); (2) in failing to notify him that it intended to reject the presentence report’s recommendation on § 2A6.1(b)(2); (3) in adding two points to his criminal history score for juvenile offenses; and (4) in inadequately informing him of the consequences of changing his plea. We affirm.
I.
In April, 1990, Sanders wrote two “letters” consisting almost entirely of racial epithets and derogatory language. He addressed the first of these letters to “N.I.G.G.E.R.S.” and mailed it to the Fairfield chapter of the National Association for the Advancement of Colored People (“the NAACP”). On the envelope, Sanders wrote ‘Watch out this might be a letter b_,” “die,” “go back to Africa,” and other derogatory remarks. In the letter itself, Sanders drew a caricature of an African-American person and wrote a variety of racial slurs.
Sanders addressed the second letter to “Jewish Pussy’s” [sic] and mailed it to the B’Nai Avraham Jewish Congregation in Fair-field (“the Jewish Congregation”). He decorated the envelope and letter with various anti-Semitic drawings, threats, and offensive phrases.
Both letters bore the return address, “Fairfield W.A.R.” (i.e. White Aryan Resistance), and a Fairfield post office box registered to Sanders. The handwriting matched Sanders’. After FBI agents confronted Sanders with the match, Sanders admitted sending both letters, explaining that he had written and mailed both letters early one morning while drunk.
*483Sanders was charged with two counts of mailing a threatening communication, a felony, 18 U.S.C. § 876, and one count of interfering with housing rights, a misdemeanor, 42 U.S.C. § 3631(a). The misdemeanor charge alleged that the NAACP office which received Sanders’ first communication was also the chapter president’s home.
Sanders initially pled guilty to Count I, mailing a threatening communication to the Jewish congregation, and Count III, interfering with housing rights.1 Based on this plea, the presentence report calculated a sentence range of ten to sixteen months and recommended a sentence of five months in custody, five months in community confinement, and three years of supervised release. However, the report also expressed an opinion that, had Sanders pled guilty to Counts I and II (the two felony mailing a threatening communication charges), rather than to Counts I and III, the applicable guidelines range would have been six to twelve months and Sanders would have been eligible for straight probation.
Sanders therefore moved to withdraw his guilty plea and substitute a new guilty plea to Counts I and II, the two felony counts of mailing a threatening communication. The government opposed this motion. However, the district court allowed Sanders to withdraw his plea, expressing concern about the misdemeanor’s factual basis and noting that the government had not presented any evidence that Sanders knew that the NAACP office was a private residence. Sanders then pled guilty to the two felonies.
A revised presentenee report calculated a guidelines range of six to twelve months and recommended that Sanders serve two months imprisonment, six months community confinement, and three years supervised release. The revised report also recommended that Sanders receive a four-level reduction in offense level because his offense “involv[ed] a single instance evidencing little or no deliberation.” U.S.S.G. § 2A6.1(b)(2). After full briefing and a hearing on the issue, however, the district court denied Sanders the four-level reduction, resulting in a guidelines range of fifteen to twenty-one months. The court sentenced Sanders to two concurrent fifteen-month prison terms followed by three years of supervised release.
II. § 2A6.1(b)(2) REDUCTION FOR A SINGLE INSTANCE EVIDENCING LITTLE OR NO DELIBERATION
Sanders first challenges the district court’s refusal to award him a four-level reduction under U.S.S.G. § 2A6.1(b)(2). We review the district court’s interpretation of the relevant guidelines de novo, accepting its underlying factual findings unless clearly erroneous. United States v. McAninch, 994 F.2d 1380, 1383 (9th Cir.), cert. denied, — U.S. —, 114 S.Ct. 394, 126 L.Ed.2d 342 (1993). United States v. Fine, 975 F.2d 596, 599 (9th Cir.1992) (en banc).
A. Single Instance
The district court found that Sanders’ conduct did not constitute a “single instance” within the meaning of § 2A6.1(b)(2) because “enough distinguishes [the letters’] preparation and mailing that they cannot be described as comprising one ‘instance.’ ” Sentencing Memorandum at 5 (Dec. 2,1993). In particular, the court noted that the letters were
addressed to two different groups of victims, they were sent to different locations, they were deposited in different mail boxes, the contents of each letter differed significantly, both were specifically tailored to the different racial or religious characteristics of the groups of intended victims, and each letter contained a different threat of violence.
Id. at 5-6.
Sanders argues that the district court misinterpreted the Guidelines, construing “single instance” as “single threat” rather than “single episode.” He relies primarily on United States v. Pacione, 950 F.2d 1348, 1356 (7th Cir.1991), cert. denied, — U.S. —, 112 S.Ct. 3054, 120 L.Ed.2d 920 (1992), in which *484the defendant twice threatened an IRS agent over the phone and then went to the IRS office an hour later and (according to a bystander) told his friend that he was going to blow up the IRS office. Id. at 1351. Sanders emphasizes that Pacione received the § 2A6.1(b)(2) reduction, despite making multiple threats, and cites the case as an indication that “offense conduct that involves multiple illegal acts may still involve a ‘single instance evidencing little or no deliberation’ within the meaning of § 2A6.1(b)(2).” Pet. R’hg at 9. According to Sanders, his conduct, like Pacione’s, took place over a few short hours and thus constitutes a “single instance” of misconduct, even if it involved several threats. ¡
While Pacione is the only published circuit opinion addressing a § 2A6.1(b)(2) reduction,2 the case is hardly controlling. The Seventh Circuit did not address the validity of the § 2A6.1(b)(2) reduction, merely mentioning the reduction in passing in discussing an unrelated issue. See Pacione, 950 F.2d at 1356. Thus, contrary to Sanders’ arguments, the Seventh Circuit did not affirm Pacione’s § 2A6.1(b)(2) reduction or hold that Pacione’s conduct constituted a “single instance evidencing little or no deliberation.”
Nonetheless, we agree that “single instance” does not necessarily mean “single threat” and that conduct involving several threats may constitute a single instance or episode within the meaning of § 2A6.1(b)(2). As Sanders argues, several related threats, depending on the circumstances, may comprise a single episode of threatening conduct.
However, the mere fact that Sanders’ conduct took place within a short time span does not automatically mean that his offense comprises a “single instance.” “Single instance” connotes not only a temporal relationship, but also a “single purpose” or “single scheme.” Especially when considered together with the “little or no deliberation” requirement, the term suggests that the reduction should apply to defendants whose threats are the product of a single impulse, or are a single thoughtless response to a particular event.
Thus, the “single instance” reduction might not be required where a defendant made several unrelated threats, involving several different victims, even if these threats occurred within a relatively short period of time. The reduction might not apply, for example, where a defendant, within a few hours, but for unrelated reasons, threatened both his ex-wife and a business associate. Likewise, it might not apply where the defendant made a number of similar threats over an extended period of time, as in Bellrichard, 801 F.Supp. at 265.
In contrast, the reduction might apply in cases such as Pacione, where the defendant threatened a single victim several times within a very short period of time, reacting throughout the misconduct to a single stressful event — in Pacione’s case, the IRS’s decision to levy his wife’s paycheck during her hospitalization for lung cancer. Pacione’s threats were all a response to one particular traumatic situation and they were all made over a short period of time.3
In contrast, Sanders’ conduct, while it took place over a period of a few hours, has no such “single motive.” He targeted two separate groups, based on two separate sets *485of prejudices, and two separate sets of motives. Although both letters express racial hatred, writing two letters to two different groups and tailoring each letter to the particular religious or racial characteristics of the group suggests less a “single instance” of aberrant conduct and more a chronic tendency to threaten persons because of their group .membership. The district court did not clearly err in finding that Sanders’ conduct did not involve a single instance of misconduct or that his two letters constituted two instances, separated not by time, but by victim.
B. Little or No Deliberation
Nor did the court err in finding that Sanders’ conduct evidenced deliberation. According to the court,
[t]he contents of the writings themselves demonstrate that some deliberation went into their preparation. Moreover, [Sanders] selected two distinct groups of victims, he selected them for their race and religion, and he tailored the contents of his letters to their race and religion. [He] then obtained the victims’ addresses, attached proper postage, and deposited the two letters in two different mail drop boxes. These actions show a deliberate thought process rather than an impulsive action.
Sentencing Memorandum at 7 (citing Bell-richard, 801 F.Supp. at 265).
Sanders alleges that the district court inferred deliberation from the ordinary and essential steps involved in mailing a letter. According to Sanders, under the district court’s interpretation of deliberation, a defendant convicted of a 18 U.S.C. § 876 violation could never receive a § 2A6.1(b)(2) reduction, as mailing a threatening communication necessarily involves addressing an envelope, affixing postage, and mailing a letter.
We agree that the mere act of mailing a letter does not, in and of itself, necessarily require deliberation. We also agree that the contents of Sanders’ letters do not evidence “deliberation” in the sense of intelligent thought — on the contrary, Sanders’ offensive racial epithets and caricatures demonstrate an obvious lack of thoughtful consideration.
However, we cannot say as a matter of law that Sanders’ letters show “little or no deliberation.” Sanders did not just mail a note to a familiar address stating “I am going to kill you.” He looked up addresses of particular organizations and selected particular victims. His letters, while relatively short, contain a variety of racist and anti-Semitic statements and drawings, tailored to each of his particular victims. These statements are calculated to frighten and upset two particular groups of victims and to imply that they should take his threats seriously. Sanders’ use of group insults and references to white supremacy groups suggests an intent to frighten numerous persons. Although writing such letters certainly does not require intelligent thought, it requires some time and attention.
The district court did not clearly err in finding that Sanders’ conduct showed deliberation. While “thought” may not be the most accurate characterization of Sanders’ mental effort, the circumstances of the letters showed some planning and a clear intent to harass the target groups.
III. NOTICE OF INTENTION TO REJECT THE PRESENTENCE REPORT
Sanders also contends that the court failed to notify him that it intended to depart from the presentenee report’s recommendation concerning § 2A6.1(b)(2). As he notes, U.S.S.G. § 6A1.3(a), p.s. requires sentencing courts to give parties “an adequate opportunity to present information” regarding “any factor important to the sentencing determination [which] is reasonably in dispute.” Moreover, § 6A1.3(b), p.s. requires courts to “resolve disputed sentencing factors in accordance with Rule 32(a)(1), Fed.R.Crim.Pro ..., notify the parties of its tentative findings and provide a reasonable opportunity for submission of oral and written objections before imposition of sentence.” See also United States v. Brady, 928 F.2d 844, 847 (9th Cir.1991) (defendant must have notice that the court intends to depart from the presentence report’s recommendation); United States v. Nuno-Para, 877 F.2d 1409, 1415 (9th Cir.1989).
*486Sanders contends that he did not learn of the district court’s intention to reject the presentence report recommendation until “the close of sentencing.” Appellant’s Br. at 13. However, the district court first questioned the applicability of § 2A6.1(b)(2) at Sanders’ change of plea hearing, more than a month before sentencing. Tr. Nov. 10, 1993 at 8. At this hearing, the government specifically indicated that it would oppose a reduction based on § 2A6.1(b)(2) and argued both that Sanders’ conduct constituted “two separate instances” and that “there was a great deal of thought taken to make these threats.” Id. at 12. Before sentencing, both parties filed briefs on the relevance of § 2A6.1(b)(2) and argued the issue to the court.
Thus, even if the district court failed to issue “tentative findings” before sentencing, Sanders had ample notice and an opportunity to litigate the § 2A1.6(b)(2) issue. Cf. United States v. Palmer, 946 F.2d 97, 100 (9th Cir.1991). Any error was harmless.
IV. CRIMINAL HISTORY POINTS FOR JUVENILE OFFENSES
Sanders next challenges his criminal history score, contending that the district court erred in adding two points for juvenile offenses. The district court accepted the pre-sentence report’s recommendation that Sanders receive one point for a 1987 California juvenile court decision declaring him a ward of the court, and one point for a 1988 decision “continuing” his wardship.4 We review de novo a district court’s determination that a prior adjudication falls within the scope of the Sentencing Guidelines. United States v. Robinson, 967 F.2d 287, 292 (9th Cir.1992).
Sanders does not dispute the fact of his juvenile adjudications, but contends that they are not convictions within the meaning of the Guidelines. As he notes, under U.S.S.G. § 4A1.2(a)(l), a prior sentence “counts” for criminal history purposes only if it was “imposed upon adjudication of guilt, whether by guilty plea, trial, or plea of nolo contendere.” See also United States v. Booten, 914 F.2d 1352, 1354 (9th Cir.1990) (defendant must have been adjudged guilty). The government bears the burden of proving the fact of a prior conviction. United States v. Newman, 912 F.2d 1119, 1122 (9th Cir. 1990).
As Sanders argues, a California juvenile adjudication is not a “conviction.” See In re Asean D., 14 Cal.App.4th 467, 17 Cal. Rptr.2d 572, 577 n. 11 (1998). However, a child may be declared a ward of the court as a “law violator” only after the government shows “beyond a reasonable doubt” that the child has violated a criminal law. Cal.Welf. & Inst.Code § 701. Thus, Sanders’ first juvenile adjudication, in which the court declared him a ward of the court, involved an adjudication of guilt and may be used in calculating his criminal history. Booten, 914 F.2d at 1355.
However, a California juvenile court may modify a wardship order without a subsequent adjudication of guilt. In re Glen J., 97 Cal.App.3d 981, 159 Cal.Rptr. 148, 151 (1979). Thus, Sanders’ second juvenile adjudication, in which the California court “continued” Sanders’ wardship, did not necessarily involve an adjudication of guilt. Absent proof that the California juvenile court found Sanders guilty beyond a reasonable doubt, the adjudication may not be used to increase Sanders’ criminal history score.
We must remand for resentencing unless “the record as a whole, [reveals] that the error was harmless, i.e. that the error did not affect the district court’s selection of the sentence imposed.” Williams v. United States, 503 U.S. 193, -, 112 S.Ct. 1112, 1121, 117 L.Ed.2d 341 (1992) (interpreting 18 U.S.C. § 3742(f)(1)); see also United States v. Rodriguez-Razo, 962 F.2d 1418, 1423-25 (9th Cir.1992) (noting that this standard imposes an “exacting burden” on the party defending the sentence).
Subtracting one point from Sanders’ criminal history score will not change Sanders’ criminal history category or the applicable guidelines range: Sanders’ previous score *487was five5 and Category III includes scores four though six. U.S.S.G. Ch. 5, Pt. A. Thus, with or without the contested point, Sanders’ sentencing range is fifteen to twenty-one months. The district court sentenced Sanders to fifteen months, the minimum under the Guidelines. Nothing in the record suggests that the court would have (or could have) imposed a lighter sentence absent the error. Thus, the error was harmless and a remand is unnecessary. Cf. United States v. Rutledge, 28 F.3d 998, 1003 (9th Cir.1994).
V. GUILTY PLEA
Finally, Sanders contends that the district court failed to warn him of the consequences of pleading guilty to the two felonies. Fed.R.Crim.P. 11(c)(1). He does not challenge the factual basis of his convictions, and specifically concedes that both letters contained a “threat” within the meaning of 18 U.S.C. § 876. Rather, he emphasizes that the presentence report led him to believe that changing his plea would reduce his sentence.6
However, before accepting Sanders’ change of plea, the district court specifically advised Sanders that “there are no assurances as to what the Guidelines will be on the two felonies.” Tr. Nov. 10, 1993 at 17-18. The court also warned that it “might even find for some reason that because there are two felonies, the Guidelines are higher than they would have been for the misdemeanor and the felony.” Id.
Sanders did not challenge the validity of his plea in the district court and has thus waived any objections except those which fall within one of the narrow exceptions to the waiver rule or constitute plain error. United States v. Flores-Payon, 942 F.2d 556, 558-60 (9th Cir.1991). Sanders has shown neither. Because the presentence report is not prepared until after the defendant pleads guilty, a court cannot “inform [a] defendant of the minimum sentence available under the guidelines” before accepting his plea. United States v. Maree, 934 F.2d 196, 200 (9th Cir. 1991). While Sanders’ disappointment is understandable, he has not shown plain error.
AFFIRMED.
. In return, the government agreed not to oppose a reduction for acceptance of responsibility or a four-level decrease for a "single instance evidencing little or no deliberation.” U.S.S.G. § 2A6.1(b)(2).
. The only other published cases even mentioning § 2A6.1(b)(2) are United States v. Lowenstein, 1 F.3d 452, 453-54 (6th Cir.1993) (affirming an upward departure where the defendant wrote a huge volume of threatening letters); United States v. Jimenez-Otero, 898 F.2d 813, 814 (1st Cir.1990) (affirming an upward adjustment under § 2A6.1(b)(1) for an “offense involv[ing] any conduct evidencing an intent to carry out such threat” where the defendant brandished a screwdriver while making the threats); United States v. Bellrichard, 801 F.Supp. 263, 266 (D.Minn.1992) (denying a § 2A6.1(b)(2) reduction where the defendant wrote a number of letters to several different victims).
. Sanders assumes that Pacione's misconduct covered at least an hour, because a bystander testified that one hour after the threatening phone call, Pacione was at the IRS office telling his friend that he was going to blow up the IRS office. However, nothing in the opinion indicates that the district court found that this statement was threat, that it was made in the presence of the IRS agent, or that it was anything but a private expression of anger. Thus, Pacione may have been sentenced solely for the two threats made during the phone call.
. According to the presentence report, the first incident involved “petty theft [and] possession of a knife,” and the latter involved a “DUI, Violation of Probation.” PSI I at 1128, ¶ 29.
. Sanders received three points for adult offenses, including a 1989 conviction for driving with a suspended license (one point) and a 1990 conviction of assault with a deadly weapon not a firearm (two points).
. Under Sanders' original plea agreement, the government promised not to contest the applicability of § 2A6.1(b)(2). Sanders lost the benefit of this agreement when he changed his plea.