When is the last frost in La Mesa, CA?

The average last spring frost (50% probability of 32°F) in La Mesa is around January 6, based on NOAA/NCEI 1991–2020 normals at the El Cajon, CA station (4.9 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 La Mesa?

The average first fall frost in La Mesa, CA is around December 21, giving roughly a 350-day frost-free growing season.

What planting zone is La Mesa, CA?

La Mesa is in USDA plant hardiness zone 10b (average annual extreme minimum temperature 35 to 40°F), from the 2023 USDA Plant Hardiness Zone Map.

What is the weather like in La Mesa?

In La Mesa, CA the warmest month is August (avg high 88.6°F) and the coldest is December (avg low 41.7°F). It averages about 11.6″ of precipitation a year.

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La Mesa, CA Planting Calendar & Frost Dates

USDA hardiness zone 10b · ZIP 91941 · elevation 151′ · NOAA & USDA data

La Mesa is in USDA hardiness zone 10b (winters can dip to 35 to 40°F), with a growing season of about 350 days between the average last spring frost (January 6) and first fall frost (December 21). The warmest month is August (avg high 88.6°F); the coldest is December (avg low 41.7°F). It averages 11.6″ 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

10b

min temp 35 to 40°F

Last spring frost

January 6

avg (50% prob, 32°F)

First fall frost

December 21

avg (50% prob, 32°F)

Growing season

350 days

frost-free window

Warmest month

August

avg high 88.6°F

Month-by-month typical weather in La Mesa

Average conditions from the NOAA/NCEI 1991–2020 U.S. Climate Normals at El Cajon, CA (4.9 mi away). Temperatures °F, precipitation & snow in inches.

Month	Avg high	Avg low	Mean	Precip (in)
January	69.3	42.5	55.9	2.3
February	69.2	44.4	56.8	2.6
March	71.3	48	59.7	1.9
April	74.5	50.7	62.6	0.8
May	76.2	55.9	66.1	0.3
June	80.8	59.4	70.1	0.1
July	86.1	63.3	74.7	0.2
August	88.6	64.7	76.6	0
September	87.3	62.1	74.7	0.1
October	81	55.6	68.3	0.5
November	75.2	47.1	61.2	1
December	68.5	41.7	55.1	1.8

What to plant when in La Mesa

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 26
Spinach	cool	Sow (spring): November 25 · Sow (fall): October 26
Lettuce	cool	Sow (spring): December 9 · Sow (fall): October 26
Kale	cool	Transplant (spring): December 16 · Sow (fall): October 12
Broccoli	cool	Transplant (spring): December 23
Carrots	cool	Sow (spring): December 16 · Sow (fall): October 12
Onions	cool	Transplant (spring): December 9
Potatoes	cool	Plant seed potatoes: December 23
Radishes	cool	Sow (spring): December 9 · Sow (fall): November 9

Dates are computed from La Mesa'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

Santee, CA National City, CA San Diego, CA El Cajon, CA Chula Vista, CA Poway, CA Encinitas, CA Escondido, CA

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 — El Cajon, CA, 4.9 mi (confidence: high). Monthly weather normals: El Cajon, CA, 4.9 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.