According to the NOAA Office of Protected Resources, a program under the U.S. Department of Commerce, salmon can weigh up to 120 pounds. This weight has been recorded for chinook salmon, the largest Pacific salmon species. On average, however, chinook weigh around 40 pounds.
PBS notes that the top weight for an individual chinook is 126 pounds, with weights around 30 pounds being more common for that species. PBS also reports that weights between 3.5 and 4 pounds are normal for pink salmon, the smallest Pacific species. The U.S. Fish and Wildlife website states that Atlantic salmon have a much smaller variation in weight, with average adult sizes being between 7 and 12 pounds.