Frost Dates for Oroville, CA 95966

Last spring frost April 20 · First fall frost November 11 · 205 frost-free days · USDA Zone 9b

Frost probability for 95966

Frost10%50%90%
Spring (last frost)May 11April 20April 29
Fall (first frost)October 20November 11November 12

Dates come from NOAA 1971–2000 freeze probabilities at the nearest reporting station (23.7 km away); the 50% date is the median year.

Frost dates by ZIP code in Oroville, CA

ZIPLast spring frost (50%)First fall frost (50%)Zone
95966April 20November 119b
95965March 6December 29b

Month by month in Oroville

MonthWhat to do
JanuaryPlan your garden layout and order seeds. Research varieties suited to your frost dates.
FebruaryStart peppers and eggplant indoors 8–10 weeks before your last frost (around April 20). Start tomatoes about two weeks later, 6–8 weeks before last frost.
MarchStart herbs, basil, and squash indoors (4–6 weeks before frost). Direct sow peas, spinach, and lettuce if soil is workable.
AprilLast frost around April 20. Transplant cold-hardy crops (broccoli, kale, cabbage). Harden off tomato and pepper seedlings.
MayFrost has passed. Transplant tomatoes, peppers, and basil outdoors. Direct sow beans, cucumbers, squash, and zucchini.
JuneSuccession plant lettuce and greens. Keep beds weeded and watered consistently.
JulyHarvest regularly to encourage production. Monitor for pests and disease.
AugustMidsummer: harvest beans, zucchini, cucumbers. Start brassica seeds indoors for fall.
SeptemberDirect sow carrots and beets for fall harvest. Start fall broccoli and kale indoors.
OctoberFirst fall frost approaching (around November 11). Transplant fall brassicas. Sow spinach, arugula, and radishes.
NovemberFirst frost around November 11. Harvest tomatoes and peppers before frost. Cover cold-hardy crops with row covers to extend the season.
DecemberHarvest remaining cold-hardy crops: kale, carrots, and beets. Plant garlic bulbs for next year.

What grows in a 205-day season

Frequently Asked Questions

What is the last frost date for Oroville, CA (ZIP 95966)?

The median last spring frost date for Oroville, CA (ZIP code 95966) is around April 20. 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 Oroville, CA?

The median first fall frost date for Oroville, CA is around November 11. 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 Oroville, CA?

The frost-free growing season in Oroville is about 205 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 Oroville, CA?

Based on frost date patterns, Oroville 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 Oroville, CA?

Start tomato seeds indoors 6–8 weeks before your last frost date (around April 20). For Oroville, that's roughly February 24 to March 9. Transplant outdoors 1–2 weeks after your last frost.

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