Frost Dates for Napa, CA 94559

Last spring frost February 22 · First fall frost December 5 · 286 frost-free days · USDA Zone 9b

Frost probability for 94559

Frost10%50%90%
Spring (last frost)April 6February 22January 29
Fall (first frost)November 5December 5January 5

Dates come from NOAA 1971–2000 freeze probabilities at the nearest reporting station (3.8 km away); the 50% date is the median year.

Month by month in Napa

MonthWhat to do
JanuaryStart herbs, basil, and squash indoors (4–6 weeks before frost). Direct sow peas, spinach, and lettuce if soil is workable.
FebruaryLast frost around February 22. Transplant cold-hardy crops (broccoli, kale, cabbage). Harden off tomato and pepper seedlings.
MarchFrost has passed. Transplant tomatoes, peppers, and basil outdoors. Direct sow beans, cucumbers, squash, and zucchini.
AprilSuccession plant lettuce and greens. Keep beds weeded and watered consistently.
MayHarvest regularly to encourage production. Monitor for pests and disease.
JuneMidsummer: harvest beans, zucchini, cucumbers. Start brassica seeds indoors for fall.
JulyDirect sow carrots and beets for fall harvest. Start fall broccoli and kale indoors.
AugustDirect sow carrots and beets for fall harvest. Start fall broccoli and kale indoors.
SeptemberDirect sow carrots and beets for fall harvest. Start fall broccoli and kale indoors.
OctoberDirect sow carrots and beets for fall harvest. Start fall broccoli and kale indoors.
NovemberFirst fall frost approaching (around December 5). Transplant fall brassicas. Sow spinach, arugula, and radishes.
DecemberFirst frost around December 5. Harvest tomatoes and peppers before frost. Cover cold-hardy crops with row covers to extend the season.

What grows in a 286-day season

Frequently Asked Questions

What is the last frost date for Napa, CA (ZIP 94559)?

The median last spring frost date for Napa, CA (ZIP code 94559) is around February 22. This is the 50th-percentile date — meaning half of all years see frost end before this date. Use the 10% and 90% dates to understand the full range of risk in your area.

What is the first fall frost date in Napa, CA?

The median first fall frost date for Napa, CA is around December 5. Plan to harvest or protect frost-sensitive crops like tomatoes and peppers at least a week before this date to avoid losses.

How long is the growing season in Napa, CA?

The frost-free growing season in Napa is about 286 days. This window — from your last spring frost to your first fall frost — is when warm-season vegetables thrive. Cold-hardy crops like kale, spinach, and peas can extend your season by weeks on either side.

What USDA hardiness zone is Napa, CA?

Based on frost date patterns, Napa falls approximately in 9b. USDA hardiness zones are determined by average annual minimum winter temperatures and guide both plant selection and planting timing for your location.

When should I start tomatoes indoors in Napa, CA?

Start tomato seeds indoors 6–8 weeks before your last frost date (around February 22). For Napa, that's roughly December 28 to January 11. Transplant outdoors 1–2 weeks after your last frost.

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