When is the last frost in Santa Rosa, CA?

The average last spring frost (50% probability of 32°F) in Santa Rosa is around February 25, based on NOAA/NCEI 1991–2020 normals at the Santa Rosa, CA station (5 mi away). Half of years it falls outside that date, so wait 1–2 weeks past it before setting out frost-tender plants.

When is the first fall frost in Santa Rosa?

The average first fall frost in Santa Rosa, CA is around December 1, giving roughly a 279-day frost-free growing season.

What planting zone is Santa Rosa, CA?

Santa Rosa is in USDA plant hardiness zone 9b (average annual extreme minimum temperature 25 to 30°F), from the 2023 USDA Plant Hardiness Zone Map.

What is the weather like in Santa Rosa?

In Santa Rosa, CA the warmest month is September (avg high 83.9°F) and the coldest is December (avg low 38.2°F). It averages about 31.5″ of precipitation a year.

Home › California › Santa Rosa

Santa Rosa, CA Planting Calendar & Frost Dates

USDA hardiness zone 9b · ZIP 95404 · elevation 51′ · NOAA & USDA data

Santa Rosa is in USDA hardiness zone 9b (winters can dip to 25 to 30°F), with a growing season of about 279 days between the average last spring frost (February 25) and first fall frost (December 1). The warmest month is September (avg high 83.9°F); the coldest is December (avg low 38.2°F). It averages 31.5″ of precipitation a year. Start cool-season crops several weeks before the last frost; wait until after it for tomatoes, peppers and other tender crops.

Hardiness zone

min temp 25 to 30°F

Last spring frost

February 25

avg (50% prob, 32°F)

First fall frost

December 1

avg (50% prob, 32°F)

Growing season

279 days

frost-free window

Warmest month

September

avg high 83.9°F

Month-by-month typical weather in Santa Rosa

Average conditions from the NOAA/NCEI 1991–2020 U.S. Climate Normals at Santa Rosa, CA (5 mi away). Temperatures °F, precipitation & snow in inches.

Month	Avg high	Avg low	Mean	Precip (in)
January	59.7	38.4	49.1	5.8
February	63.6	40	51.8	6.4
March	66.9	41.9	54.4	4.3
April	70.6	43.9	57.3	2
May	74.5	47.8	61.1	1.3
June	80.2	51.1	65.6	0.3
July	81.6	52.1	66.9	0
August	83	52.5	67.7	0
September	83.9	51	67.5	0.2
October	78.9	47.6	63.3	1.6
November	67.1	42	54.6	3.3
December	59	38.2	48.6	6.5

What to plant when in Santa Rosa

Crop	Season	What to do & when
Tomatoes	warm	Start seeds indoors: January 14 · Transplant out: March 4
Peppers	warm	Start seeds indoors: December 31 · Transplant out: March 11
Cucumbers	warm	Direct sow: March 4
Zucchini / squash	warm	Direct sow: March 4
Bush beans	warm	Direct sow: March 4
Sweet corn	warm	Direct sow: March 4
Basil	warm	Transplant out: March 4
Peas	cool	Sow (spring): January 21 · Sow (fall): October 6
Spinach	cool	Sow (spring): January 14 · Sow (fall): October 6
Lettuce	cool	Sow (spring): January 28 · Sow (fall): October 6
Kale	cool	Transplant (spring): February 4 · Sow (fall): September 22
Broccoli	cool	Transplant (spring): February 11
Carrots	cool	Sow (spring): February 4 · Sow (fall): September 22
Onions	cool	Transplant (spring): January 28
Potatoes	cool	Plant seed potatoes: February 11
Radishes	cool	Sow (spring): January 28 · Sow (fall): October 20

Dates are computed from Santa Rosa's average frost dates using standard cool-/warm-season timing. They're a starting point — a cold spring, a warm microclimate, or a fast-maturing variety can shift them by a week or two.

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Gear that helps you plant on time

Some links below are Amazon affiliate links (tag theboringthin-20). If you buy through them we may earn a small commission at no extra cost to you — it keeps this almanac free. We only list generic, genuinely-useful categories.

Soil thermometer →Know when the ground is warm enough to sow — the honest signal, not the calendar.Seed-starting trays + dome →Start tomatoes & peppers indoors on the schedule below.Seedling heat mat →Warms the soil for faster, more even germination indoors.Floating row cover / frost cloth →Buys you 4–8°F to beat an early or late frost.Raised garden bed kit →Warms and drains faster in spring than in-ground soil.Garden gloves →Basic kit for transplant day.

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Sources & method. Hardiness zone: 2023 USDA Plant Hardiness Zone Map (PRISM Climate Group, Oregon State University). Frost dates & growing season: NOAA/NCEI 1991–2020 U.S. Climate Normals, nearest station with published freeze normals — Santa Rosa, CA, 5 mi (confidence: high). Monthly weather normals: Santa Rosa, CA, 5 mi (confidence: high). ZIP centroid from U.S. Census 2023 ZCTA data. Frost dates are the 50%-probability date — half of years frost occurs outside the stated date. Nothing here is invented; where the nearest station is far, we say so. Last updated 2026-07-22.