When is the last frost in Harlingen, TX?

The average last spring frost (50% probability of 32°F) in Harlingen is around January 8, based on NOAA/NCEI 1991–2020 normals at the Harlingen Rio Grande Ap, TX 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 Harlingen?

The average first fall frost in Harlingen, TX is around December 29, giving roughly a 357-day frost-free growing season.

What planting zone is Harlingen, TX?

Harlingen 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 Harlingen?

In Harlingen, TX the warmest month is August (avg high 97.8°F) and the coldest is January (avg low 51.1°F). It averages about 28.2″ of precipitation a year.

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Harlingen, TX Planting Calendar & Frost Dates

USDA hardiness zone 10a · ZIP 78550 · elevation 12′ · NOAA & USDA data

Harlingen is in USDA hardiness zone 10a (winters can dip to 30 to 35°F), with a growing season of about 357 days between the average last spring frost (January 8) and first fall frost (December 29). The warmest month is August (avg high 97.8°F); the coldest is January (avg low 51.1°F). It averages 28.2″ 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

10a

min temp 30 to 35°F

Last spring frost

January 8

avg (50% prob, 32°F)

First fall frost

December 29

avg (50% prob, 32°F)

Growing season

357 days

frost-free window

Warmest month

August

avg high 97.8°F

Month-by-month typical weather in Harlingen

Average conditions from the NOAA/NCEI 1991–2020 U.S. Climate Normals at Harlingen, TX (3.7 mi away). Temperatures °F, precipitation & snow in inches.

Month	Avg high	Avg low	Mean	Precip (in)	Snow (in)
January	71.7	51.1	61.4	1.2	0
February	76	54.8	65.4	1.2	0
March	81	60	70.5	1.5	0
April	86.4	65.9	76.1	2.3	0
May	91.1	71.8	81.5	2.7	0
June	95.4	75.9	85.6	2.4	0
July	96.6	76.9	86.8	2.4	0
August	97.8	76.8	87.3	2.1	0
September	93.1	73.6	83.4	5.8	0
October	88	66.8	77.4	3.1	0
November	79.7	58.8	69.3	2	0
December	73.2	52.5	62.8	1.6	0.1

What to plant when in Harlingen

Crop	Season	What to do & when
Tomatoes	warm	Start seeds indoors: November 27 · Transplant out: January 15
Peppers	warm	Start seeds indoors: November 13 · Transplant out: January 22
Cucumbers	warm	Direct sow: January 15
Zucchini / squash	warm	Direct sow: January 15
Bush beans	warm	Direct sow: January 15
Sweet corn	warm	Direct sow: January 15
Basil	warm	Transplant out: January 15
Peas	cool	Sow (spring): December 4 · Sow (fall): November 3
Spinach	cool	Sow (spring): November 27 · Sow (fall): November 3
Lettuce	cool	Sow (spring): December 11 · Sow (fall): November 3
Kale	cool	Transplant (spring): December 18 · Sow (fall): October 20
Broccoli	cool	Transplant (spring): December 25
Carrots	cool	Sow (spring): December 18 · Sow (fall): October 20
Onions	cool	Transplant (spring): December 11
Potatoes	cool	Plant seed potatoes: December 25
Radishes	cool	Sow (spring): December 11 · Sow (fall): November 17

Dates are computed from Harlingen'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 — Harlingen Rio Grande Ap, TX, 2 mi (confidence: high). Monthly weather normals: Harlingen, TX, 3.7 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.