When is the last frost in Flagstaff, AZ?

The average last spring frost (50% probability of 32°F) in Flagstaff is around June 11, based on NOAA/NCEI 1991–2020 normals at the Ft Valley, AZ station (6.4 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 Flagstaff?

The average first fall frost in Flagstaff, AZ is around September 25, giving roughly a 99-day frost-free growing season.

What planting zone is Flagstaff, AZ?

Flagstaff is in USDA plant hardiness zone 6a (average annual extreme minimum temperature -10 to -5°F), from the 2023 USDA Plant Hardiness Zone Map.

What is the weather like in Flagstaff?

In Flagstaff, AZ the warmest month is July (avg high 81.6°F) and the coldest is January (avg low 11.3°F). It averages about 20.2″ of precipitation a year and 72.6″ of snow.

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Flagstaff, AZ Planting Calendar & Frost Dates

USDA hardiness zone 6a · ZIP 86001 · elevation 2180′ · NOAA & USDA data

Flagstaff is in USDA hardiness zone 6a (winters can dip to -10 to -5°F), with a growing season of about 99 days between the average last spring frost (June 11) and first fall frost (September 25). The warmest month is July (avg high 81.6°F); the coldest is January (avg low 11.3°F). It averages 20.2″ of precipitation a year and 72.6″ 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

min temp -10 to -5°F

Last spring frost

June 11

avg (50% prob, 32°F)

First fall frost

September 25

avg (50% prob, 32°F)

Growing season

99 days

frost-free window

Warmest month

July

avg high 81.6°F

Month-by-month typical weather in Flagstaff

Average conditions from the NOAA/NCEI 1991–2020 U.S. Climate Normals at Bellemont Wfo, AZ (9.3 mi away). Temperatures °F, precipitation & snow in inches.

Month	Avg high	Avg low	Mean	Precip (in)	Snow (in)
January	43.9	11.3	27.6	2	16.6
February	45.6	15.4	30.5	2.2	16.8
March	52.6	20.2	36.4	1.8	11.6
April	58.7	24	41.4	1.1	4.7
May	68.1	29.5	48.8	0.7	1.6
June	78.9	35.9	57.4	0.3	0
July	81.6	46.4	64	2.7	0
August	79.2	45.9	62.6	3.2	0
September	74	37.3	55.7	1.8	0
October	63.8	26.8	45.3	1.6	1.3
November	52.5	18.2	35.4	1.2	5.5
December	43.7	11.3	27.5	1.8	14.5

What to plant when in Flagstaff

Crop	Season	What to do & when
Tomatoes	warm	Start seeds indoors: April 30 · Transplant out: June 18
Peppers	warm	Start seeds indoors: April 16 · Transplant out: June 25
Cucumbers	warm	Direct sow: June 18
Zucchini / squash	warm	Direct sow: June 18
Bush beans	warm	Direct sow: June 18
Sweet corn	warm	Direct sow: June 18
Basil	warm	Transplant out: June 18
Peas	cool	Sow (spring): May 7 · Sow (fall): July 31
Spinach	cool	Sow (spring): April 30 · Sow (fall): July 31
Lettuce	cool	Sow (spring): May 14 · Sow (fall): July 31
Kale	cool	Transplant (spring): May 21 · Sow (fall): July 17
Broccoli	cool	Transplant (spring): May 28
Carrots	cool	Sow (spring): May 21 · Sow (fall): July 17
Onions	cool	Transplant (spring): May 14
Potatoes	cool	Plant seed potatoes: May 28
Radishes	cool	Sow (spring): May 14 · Sow (fall): August 14

Dates are computed from Flagstaff'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 — Ft Valley, AZ, 6.4 mi (confidence: high). Monthly weather normals: Bellemont Wfo, AZ, 9.3 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.