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Regional Calendars, Climate & DataCrop Calendar for California’s Central Valley
The Central Valley has mild winters, hot, dry summers and a growing season that can run most of the year. The calendar is shaped by irrigation, heat and winter chill rather than by frost alone.
Key points
- Temperature ranges, not calendar dates, define planting windows for cool-season and warm-season crops.
- Hot, dry summers make irrigation central, so confirm local water rules and allocations.
- Plan cool-season crops to mature before heat and long days cause bolting.
- Tree and vine crops need varieties matched to local winter chill and bloom-time frost risk.
- Keep records of heat events and planting results to refine your own windows.
What makes the Central Valley calendar unusual?
Summers are hot and dry, so nearly every crop depends on irrigation. Winters are mild but still bring frost in many places, especially in low spots on clear nights. The long season allows cool-season vegetables in fall, winter and spring, and warm-season crops in summer.
Because the valley is large and varied, from the north to the south, local guidance matters more than any regional table.
Fog and cool air in parts of the valley can also matter, since they affect temperature at bloom and the length of the warm period for heat-loving crops. Ask your local advisor how this plays out in your area.
How does temperature guide timing?
UC Agriculture and Natural Resources explains that temperature is the key factor in timing planting in California. Cool-season crops such as lettuce, spinach, broccoli and carrots grow best at about 55 to 75 degrees F and tolerate slight frosts, while warm-season crops such as tomatoes, squash, corn and melons prefer about 65 to 95 degrees F. Planting too early or too late reduces productivity.
The same source gives regional planting tables that are approximate, and it advises knowing your approximate first and last frost dates.
Plan for heat as well as cold. Midsummer heat can slow fruit set and stress leaf crops, so many growers shift sensitive plantings earlier or later and use shade or other protection.
- Cool-season crops: about 55 to 75 degrees F
- Warm-season crops: about 65 to 95 degrees F
- Match planting to temperature, not just to the month
What about day length and bolting?
UC ANR notes that many annuals, including radishes, lettuce and spinach, tend to flower as days lengthen in late spring. In a long, warm season, that means cool-season crops are best planted so they mature before the heat and long days push them to bolt.
Choose bolt-resistant varieties for later plantings and check seed catalog guidance.
Seed and transplant timing matter in heat. Hot soil can reduce germination of some cool-season crops, so extension guides often suggest shade, moisture management or adjusted dates for late-summer seeding. Seed catalogs and extension guides list bolt tolerance and heat tolerance by variety, so read those notes before choosing a late planting.
How should you plan irrigation and water?
Water supply drives the calendar. Allocations, district schedules and groundwater rules vary by location and by year, so confirm your local water rules before planning acreage. Schedule irrigation by soil moisture and crop stage, using a water balance approach where possible.
Heat waves raise crop water use quickly, so keep capacity in reserve for peak demand.
Check district rules about water delivery schedules, since a gap in supply during a hot week can matter more than the schedule on paper.
What about orchards and winter chill?
Many tree and vine crops in the valley need a period of winter cold to break dormancy properly, and bloom-time frost is a risk once buds open. Choose varieties suited to your local winter chill and frost pattern, and ask extension about frost protection options for your site.
Tree crop decisions last for decades, so review local records and extension advice before planting.
How do you build a calendar for your own acreage?
List your crops, mark the months when temperatures fit their range, and overlay frost risk and heat stress periods. Add water availability by month. Compare with the UC ANR regional planting table and adjust for your microclimate, since even small distances can differ, as the UC source cautions.
Keep notes on planting date, stand, heat events and harvest each year, and refine the calendar from them. Share your notes with your advisor each year so planting tables for your area can improve.
What records should you keep in a long, warm season?
Because the season is so long, it is easy to lose track of what worked. Record planting date, variety, irrigation, heat events and harvest dates for each planting, and note when crops bolted, sunburned or lost quality.
After a couple of years, those notes will show which planting windows consistently work on your soil and which only look good on paper. They also help when you discuss crop and water plans with your advisor or buyer.
Sources and further reading
Last reviewed: November 2026. Educational information, ranges only. Confirm timing with your county extension office.