This is an action on an alleged breach of a written contract.
On March 9, 1968, the plaintiff, Richard T. Stender, a pea grower, entered into a written contract with the defendant, Twin City Foods, Inc., a food processor. This contract was a mimeographed form prepared by the defendant and signed by both parties.
Under the terms of the contract, the plaintiff was required to plant, fertilize and cultivate 120 acres of “Perfection” peas, the seed of which was supplied by the defendant. In turn, the defendant was obligated to harvest and vine the peas at their proper maturity and pay a stipulated price for them, depending upon the quality of tenderness of the peas.
The defendant executed similar contracts with other pea growers; and, having first planted peas in 1959, the plaintiff was an experienced grower with knowledge that the defendant executed these similar contracts.
Under the agreement, the defendant made an assignment of planting dates which were routinely staggered so that various seed crops would mature at different times, thus allowing the defendant to harvest the crops of all its contract growers in a systematic manner. The plaintiff was assigned April 28 and 29, 1968 as planting dates on a 55-acre tract and May 11 and 12,1968 on a 65-acre tract.
Relative to the scheduling of crops, part 3, section 12 of the contract provides:
In Twin City scheduling of time for cutting and delivery, Twin City does not guarantee selection of most desirable time for maximum return of grade or tonnage and is obligated only to schedule crops in good faith for efficient harvesting and handling of the crop contracted hereby and by other similar contracts with other growers.
(Italics ours.)
The first planting of the 55-acre tract came to maturity and was properly harvested and vined by the defendant on *252July 23, 1968. Of the remaining 65-acre tract, there were 2 acres which were blighted by wilt, leaving 63 acres of peas which became ready for harvesting in the period between July 27 and August 2, 1968. At this time, this block of 63 acres was bypassed by the defendant and the peas were not harvested.
The plaintiff brought the present action to recover damages for the failure of the defendant to harvest and vine the peas on this acreage, and for improperly bypassing and leaving the peas in the field. The plaintiff sought to recover $251 per acre or $15,213, the amount which the plaintiff would have received if the crop had been harvested by the defendant.
Defendant’s excuse for nonperformance in harvesting the peas was based upon part 5, section 1 of the contract, which provides:
In the event of circumstances resulting from adverse weather conditions, mechanical failures or other means that may delay harvest of the green pea crop beyond the optimum maturity for processing, Twin City has the option to divert that portion of Grower’s acreage for seed or feed purposes as the quality of the salvage may dictate.
(Italics ours.)
The trial court found that the number of peas ready for harvest at the time of optimum maturity for processing exceeded the expectations of the defendant processor and that the reason for the excess was adverse weather conditions. Accordingly, judgment was entered allowing the plaintiff recovery of $6,615, with interest, for damages computed on the basis of a permissible bypass and for dry peas. The plaintiff’s complaint for general damages for failure to harvest and process the pea crop for freezing purposes was dismissed.
The issue raised on appeal is whether there was sufficient evidence for the trial court to find that the “adverse weather” condition was met, so as to excuse the defendant’s duty to perform its contractual obligation to harvést the plaintiff’s pea crop.
*253The trial court made the following findings of fact. The adverse weather conditions consisted of an unusual, unexpected and severe fluctuation of ambient temperatures which prevented the routine scheduled maturing of the entire pea crop under contract to the defendant, of which entire crop plaintiff’s 63 acres constituted a part. In the period from July 12-20, 1968, the ambient temperatures were lower than normal, generally in the 60-degree range which had the effect of retarding maturation of the peas. From July 21-25, 1968, the ambient temperatures gradually increased, which started the peas “moving” toward maturity. From July 26-August 2, 1968, the ambient temperatures increased rapidly and substantially info the 80-degree range, which snapped all the peas to maximum maturity at the same time, rather than on the scheduled chronological series of ripening and maturity as had been planned and expected.1 As all the peas unexpectedly matured within an extremely short period of time, the defendant was unable to harvest all the peas of its contract growers and elected to bypass some of the peas.
There is substantial evidence in the record to support this finding. The record contains a recordation of the maximum and minimum temperatures from July 12 through August 2, 1968. Six witnesses appeared at the trial and five indicated that the weather pattern experienced during July and early August of 1968 was unusual and adverse, and one witness failed to testify on the point. The trial court’s findings of fact, if supported by substantial evidence, should not be disturbed on appeal. Thorndike v. *254Hesperian Orchards, Inc., 54 Wn.2d 570, 343 P.2d 183 (1959); Zillah Feed Yards, Inc. v. Carlisle, 72 Wn.2d 240, 432 P.2d 650 (1967); Lindbrook Constr., Inc. v. Mukilteo School Dist. 6, 76 Wn.2d 539, 458 P.2d 1 (1969); Noah v. Montford, 77 Wn.2d 459, 463 P.2d 129 (1969); Sylvester v. Imhoff, 81 Wn.2d 637, 503 P.2d 734 (1972).
Resort must be made to the rules of construction and interpretation in examining the bypass provision of part 5, section 1 of the contract in question.
The writing in question is clearly integrated (part 3, section 12 of the contract). A contract provision must be read in pari materia with the whole contract and in light of all the circumstances surrounding the contract. Henry v. Lind, 76 Wn.2d 199, 455 P.2d 927 (1969).
Determination of the intent of the contracting parties is to be accomplished by viewing the contract as a whole, the subject matter and objective of the contract, all the circumstances surrounding the making of the contract, the subsequent acts and conduct of the parties to the contract, and the reasonableness of respective interpretations advocated by the parties. Jacoby v. Grays Harbor Chair & Mfg. Co., 77 Wn.2d 911, 468 P.2d 666 (1970); Ramsey v. Sedlar, 75 Wn.2d 901, 454 P.2d 416 (1969); Schauerman v. Haag, 68 Wn.2d 868, 416 P.2d 88 (1966); Dickson v. Hausman, 68 Wn.2d 368, 413 P.2d 378 (1966).
Both the plaintiff and the defendant were heavily involved in the Washington pea industry, plaintiff as a grower with 8 years of experience and the defendant as a large processor. This fact would indicate that the contract should be construed in light of the usages of the pea industry existing at the time the contract was executed.
As the trial court indicated, it was the well established plan of all the pea processors in the Skagit County area to plant the peas in a staggered manner in order to avoid the entire crop maturing at once. This system was in wide use and known by all the individual growers. In fact, the plaintiff testified as to his knowledge of the custom of staggered planting and the planning and calculation of harvest sched*255uling. Thus, the plaintiff must be held to have had knowledge of the existence of other pea contracts with Twin City-Foods, the staggered planting schedule and the reasons therefor.
There is substantial evidence in the record indicating that the weather experienced during the month of July, 1968 was unusual and adverse to the growing and harvesting of peas in that it was the direct cause of the bypassing that occurred in the pea industry that year. Stokely, Libby, McNeill & Libby and National Fruit Can Company, in addition to Twin City Foods, bypassed pea acreage. The only processor or grower appearing at the trial and not experiencing problems in 1968 was Cedargreen Foods. However, at no point did the testimony of the representative of this latter company deal with the disputed findings that the weather conditions were unusual and adverse.
The record supports the trial court’s conclusion that the reason that the defendant bypassed the plaintiff’s crop is that the weather conditions increased the size of the crops ready for processing beyond any reasonable expectations.
The provisions of the written contract require both parties to make a good faith effort to perform. The findings of fact of the trial court reflect the good faith effort of the defendant. Every effort was made by the defendant to acquire additional vining equipment from eastern Washington, Oregon and other areas. The normal number of viners in the Skagit County area was 68, a number sufficient to harvest the entire contract crop under normal circumstances. Because of the unusual weather conditions, the defendant brought in 28 additional viners to supplement its normal complement, but even the 96 viners proved insufficient to avoid bypassing some acreage. And, as the record discloses, the bypassing was not arbitrary, but was carried out in a systematic manner based, as closely as possible, on the original harvesting schedules.
The definition of adverse weather conditions must be determined in light of reasonable industry custom and usage. Once a contract is established, usage and custom are *256admissible into evidence to explain the terms of the contract. Milone & Tucci, Inc. v. Bona Fide Builders, Inc., 49 Wn.2d 363, 301 P.2d 759 (1956). And, parol evidence is admissible to establish a trade usage even though words in their ordinary or legal meaning are unambiguous. Simons v. Stokely Foods, 35 Wn.2d 920, 216 P.2d 215 (1950). In view of custom and usage of the pea industry, it can be most reasonably stated that the term “adverse weather conditions” includes unusual temperature fluctuations resulting in an unexpected maturation of an entire pea crop which has been systematically planted with the objective of partial maturation over a period of time to allow for orderly harvesting. This construction of the term in question is especially valid when both parties to the contract were well aware that the purpose of scheduling crops was to avoid maturity of all the contract crops at once and to provide for systematic harvesting.
The contract provides for payment for pea crops which are harvested beyond the optimum maturity for freezing as a processed food by the defendant. The trial court properly awarded plaintiff damages computed on the basis of a permissible bypass of the plaintiff’s crop, as provided by the parties’ contract.
Judgment of the trial court is affirmed, and judgment of the Court of Appeals is hereby reversed.
Finley, Hamilton, Stafford, and Utter, JJ., concur.
The maximum and minimum temperatures from July 12 through August 2,1968 were as follows: