Clarissa Reyes, Orchard Systems Advisor, Sutter, Yuba, Butte and Placer counties

Peach harvest can be predicted fairly accurately by the temperatures in the first 30 days following bloom. Other factors such as weather near harvest, soil, tree nutrition, and water status can also have some effect on harvest date. On average, we accumulate about 6,000 growing degree hours (GDH) during the first 30 days after bloom. Accumulation of much more than 6,000 GDH in the first 30 days after bloom leads to earlier harvest dates and smaller fruit size under normal thinning practices.

The UC Davis Fruit & Nut Information Center hosts a peach harvest prediction model that calculates GDH based on CIMIS stations and predicts harvest dates of select cultivars.

Full bloom for Sutter-Yuba this year was March 3. Given the early bloom and warm temperatures throughout March, harvest will likely be very early this year. To achieve the best fruit size possible in this shortened amount of time to harvest, it is best to thin early, which allows for more resources to reach each remaining fruit, compared to if you wait to thin later.

Table 1. Historical full bloom dates for Sutter-Yuba counties, growing degree hours 30 days after bloom since 2003 and a very early harvest prediction for 2026.