When is the last frost in Cupertino, CA?

The average last spring frost (50% probability of 32°F) in Cupertino is around March 21, based on NOAA/NCEI 1991–2020 normals at the Skyline Ridge Preserve, CA station (5.7 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 Cupertino?

The average first fall frost in Cupertino, CA is around December 15, giving roughly a 275-day frost-free growing season.

What planting zone is Cupertino, CA?

Cupertino 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 Cupertino?

In Cupertino, CA the warmest month is July (avg high 84.9°F) and the coldest is January (avg low 39.5°F). It averages about 22.2″ of precipitation a year.

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Cupertino, CA Planting Calendar & Frost Dates

USDA hardiness zone 9b · ZIP 95014 · elevation 111′ · NOAA & USDA data

Cupertino is in USDA hardiness zone 9b (winters can dip to 25 to 30°F), with a growing season of about 275 days between the average last spring frost (March 21) and first fall frost (December 15). The warmest month is July (avg high 84.9°F); the coldest is January (avg low 39.5°F). It averages 22.2″ 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

March 21

avg (50% prob, 32°F)

First fall frost

December 15

avg (50% prob, 32°F)

Growing season

275 days

frost-free window

Warmest month

July

avg high 84.9°F

Month-by-month typical weather in Cupertino

Average conditions from the NOAA/NCEI 1991–2020 U.S. Climate Normals at Los Gatos, CA (8.6 mi away). Temperatures °F, precipitation & snow in inches.

Month	Avg high	Avg low	Mean	Precip (in)
January	58.5	39.5	49	5
February	61.9	41.3	51.6	4.9
March	66.3	43.1	54.7	3.4
April	70.3	45.1	57.7	1.4
May	75.5	49.4	62.4	0.5
June	81.7	52.5	67.1	0.2
July	84.9	55.9	70.4	0
August	84.5	55.8	70.2	0
September	82.7	53.8	68.2	0.1
October	75.5	48.9	62.2	0.8
November	64.6	42.7	53.6	2
December	57.7	39.5	48.6	4

What to plant when in Cupertino

Crop	Season	What to do & when
Tomatoes	warm	Start seeds indoors: February 7 · Transplant out: March 28
Peppers	warm	Start seeds indoors: January 24 · Transplant out: April 4
Cucumbers	warm	Direct sow: March 28
Zucchini / squash	warm	Direct sow: March 28
Bush beans	warm	Direct sow: March 28
Sweet corn	warm	Direct sow: March 28
Basil	warm	Transplant out: March 28
Peas	cool	Sow (spring): February 14 · Sow (fall): October 20
Spinach	cool	Sow (spring): February 7 · Sow (fall): October 20
Lettuce	cool	Sow (spring): February 21 · Sow (fall): October 20
Kale	cool	Transplant (spring): February 28 · Sow (fall): October 6
Broccoli	cool	Transplant (spring): March 7
Carrots	cool	Sow (spring): February 28 · Sow (fall): October 6
Onions	cool	Transplant (spring): February 21
Potatoes	cool	Plant seed potatoes: March 7
Radishes	cool	Sow (spring): February 21 · Sow (fall): November 3

Dates are computed from Cupertino'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 — Skyline Ridge Preserve, CA, 5.7 mi (confidence: high). Monthly weather normals: Los Gatos, CA, 8.6 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.