When is the last frost in San Bernardino, CA?

The average last spring frost (50% probability of 32°F) in San Bernardino is around May 5, based on NOAA/NCEI 1991–2020 normals at the Lake Arrowhead, CA station (9.5 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 San Bernardino?

The average first fall frost in San Bernardino, CA is around November 2, giving roughly a 176-day frost-free growing season.

What planting zone is San Bernardino, CA?

San Bernardino 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 San Bernardino?

In San Bernardino, CA the warmest month is August (avg high 81.8°F) and the coldest is January (avg low 28.7°F). It averages about 37.7″ of precipitation a year and 22.4″ of snow.

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San Bernardino, CA Planting Calendar & Frost Dates

USDA hardiness zone 10a · ZIP 92405 · elevation 1587′ · NOAA & USDA data

San Bernardino is in USDA hardiness zone 10a (winters can dip to 30 to 35°F), with a growing season of about 176 days between the average last spring frost (May 5) and first fall frost (November 2). The warmest month is August (avg high 81.8°F); the coldest is January (avg low 28.7°F). It averages 37.7″ of precipitation a year and 22.4″ of snow, mostly mid-winter. 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

May 5

avg (50% prob, 32°F)

First fall frost

November 2

avg (50% prob, 32°F)

Growing season

176 days

frost-free window

Warmest month

August

avg high 81.8°F

Month-by-month typical weather in San Bernardino

Average conditions from the NOAA/NCEI 1991–2020 U.S. Climate Normals at Lake Arrowhead, CA (9.5 mi away). Temperatures °F, precipitation & snow in inches.

Month	Avg high	Avg low	Mean	Precip (in)	Snow (in)
January	44.4	28.7	36.5	8.4	3
February	44.9	29.8	37.4	9.9	5.3
March	52	31.6	41.8	5.2	6.7
April	60	36.1	48	2.8	2.8
May	67	40.8	53.9	1.2	0.8
June	76.4	49.1	62.8	0.3	0
July	81.1	57.1	69.1	0.1	0
August	81.8	57.1	69.4	0.1	0
September	74.2	51.9	63	0.3	0
October	63	42.8	52.9	2.1	0
November	51.5	33.8	42.7	2.4	0.3
December	43	29.1	36	5.2	3.5

What to plant when in San Bernardino

Crop	Season	What to do & when
Tomatoes	warm	Start seeds indoors: March 24 · Transplant out: May 12
Peppers	warm	Start seeds indoors: March 10 · Transplant out: May 19
Cucumbers	warm	Direct sow: May 12
Zucchini / squash	warm	Direct sow: May 12
Bush beans	warm	Direct sow: May 12
Sweet corn	warm	Direct sow: May 12
Basil	warm	Transplant out: May 12
Peas	cool	Sow (spring): March 31 · Sow (fall): September 7
Spinach	cool	Sow (spring): March 24 · Sow (fall): September 7
Lettuce	cool	Sow (spring): April 7 · Sow (fall): September 7
Kale	cool	Transplant (spring): April 14 · Sow (fall): August 24
Broccoli	cool	Transplant (spring): April 21
Carrots	cool	Sow (spring): April 14 · Sow (fall): August 24
Onions	cool	Transplant (spring): April 7
Potatoes	cool	Plant seed potatoes: April 21
Radishes	cool	Sow (spring): April 7 · Sow (fall): September 21

Dates are computed from San Bernardino'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.

Nearby cities in California

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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 — Lake Arrowhead, CA, 9.5 mi (confidence: high). Monthly weather normals: Lake Arrowhead, CA, 9.5 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.