When is the last frost in Sunnyvale, CA?

The average last spring frost (50% probability of 32°F) in Sunnyvale is around January 6, based on NOAA/NCEI 1991–2020 normals at the Moffett Federal Airfield, CA station (2 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 Sunnyvale?

The average first fall frost in Sunnyvale, CA is around December 23, giving roughly a 353-day frost-free growing season.

What planting zone is Sunnyvale, CA?

Sunnyvale is in USDA plant hardiness zone 10a (average annual extreme minimum temperature 30 to 35°F), from the 2023 USDA Plant Hardiness Zone Map.

What is the weather like in Sunnyvale?

In Sunnyvale, CA the warmest month is August (avg high 82.7°F) and the coldest is December (avg low 42.8°F). It averages about 16.1″ of precipitation a year.

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Sunnyvale, CA Planting Calendar & Frost Dates

USDA hardiness zone 10a · ZIP 94085 · elevation 20′ · NOAA & USDA data

Sunnyvale is in USDA hardiness zone 10a (winters can dip to 30 to 35°F), with a growing season of about 353 days between the average last spring frost (January 6) and first fall frost (December 23). The warmest month is August (avg high 82.7°F); the coldest is December (avg low 42.8°F). It averages 16.1″ 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

10a

min temp 30 to 35°F

Last spring frost

January 6

avg (50% prob, 32°F)

First fall frost

December 23

avg (50% prob, 32°F)

Growing season

353 days

frost-free window

Warmest month

August

avg high 82.7°F

Month-by-month typical weather in Sunnyvale

Average conditions from the NOAA/NCEI 1991–2020 U.S. Climate Normals at San Jose, CA (6.8 mi away). Temperatures °F, precipitation & snow in inches.

Month	Avg high	Avg low	Mean	Precip (in)
January	59	43.3	51.1	3
February	62.8	45.4	54.1	3.2
March	66.4	47.6	57	2.6
April	70	49.8	59.9	1.2
May	74.9	53.3	64.1	0.5
June	80.1	57	68.5	0.2
July	82.2	59.1	70.6	0
August	82.7	59.8	71.2	0
September	81.4	58.2	69.8	0.1
October	74.6	53.8	64.2	0.8
November	65	47.2	56.1	1.4
December	58.8	42.8	50.8	3.1

What to plant when in Sunnyvale

Crop	Season	What to do & when
Tomatoes	warm	Start seeds indoors: November 25 · Transplant out: January 13
Peppers	warm	Start seeds indoors: November 11 · Transplant out: January 20
Cucumbers	warm	Direct sow: January 13
Zucchini / squash	warm	Direct sow: January 13
Bush beans	warm	Direct sow: January 13
Sweet corn	warm	Direct sow: January 13
Basil	warm	Transplant out: January 13
Peas	cool	Sow (spring): December 2 · Sow (fall): October 28
Spinach	cool	Sow (spring): November 25 · Sow (fall): October 28
Lettuce	cool	Sow (spring): December 9 · Sow (fall): October 28
Kale	cool	Transplant (spring): December 16 · Sow (fall): October 14
Broccoli	cool	Transplant (spring): December 23
Carrots	cool	Sow (spring): December 16 · Sow (fall): October 14
Onions	cool	Transplant (spring): December 9
Potatoes	cool	Plant seed potatoes: December 23
Radishes	cool	Sow (spring): December 9 · Sow (fall): November 11

Dates are computed from Sunnyvale'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 — Moffett Federal Airfield, CA, 2 mi (confidence: high). Monthly weather normals: San Jose, CA, 6.8 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.