Ajo, AZ Frost Dates & Growing Season

The two dates every Ajo garden is planned around, plus ready-computed planting windows for the most popular crops.

Last spring frost
Jan 10
~50% chance of frost after
First fall frost
Dec 21
~50% chance of frost before
Growing season
345 days
frost-free stretch
USDA zone
≈ 9b
estimated from nearby reference
Risky (1 year in 10)MedianSafe (9 years in 10)
Last spring frost Dec 11 Jan 10 Feb 15
First fall frost Jan 24 Dec 21 Nov 25
Hard freeze (28°F), median last Jan 8 · first Jan 3

Computed from NOAA 1991–2020 climate normals at the AJO station. "Safe" means frost past that date happens only about one year in ten. Your exact garden can still run days either way with elevation and terrain — check your own ZIP with the frost date lookup.

Planting windows for Ajo

Computed from Ajo's own frost dates. Click any crop for the full zone-9 growing guide — varieties, spacing, fall plantings, and more.

CropStart seeds indoorsTransplantDirect sow
🍅 Tomatoes Nov 15 – Nov 29 Jan 17 – Jan 24
🫑 Peppers Nov 1 – Nov 15 Jan 24 – Jan 31
🥬 Lettuce Nov 29 – Dec 13 Dec 13 – Dec 27 Dec 13 – Jan 10
🫛 Peas Nov 29 – Dec 13
🥕 Carrots Dec 20 – Jan 10
🥦 Broccoli Nov 22 – Dec 6 Dec 20 – Jan 3
🥬 Kale Nov 29 – Dec 13 Dec 13 – Dec 27 Dec 13 – Dec 27
🥒 Cucumbers Dec 13 – Dec 20 Jan 17 – Jan 24 Jan 17 – Jan 24
🥒 Zucchini Dec 13 – Dec 20 Jan 17 – Jan 24 Jan 17 – Jan 24
🫘 Green Beans (Bush) Jan 17 – Jan 24
🌽 Sweet Corn Jan 17 – Jan 24
🌿 Basil Nov 29 – Dec 13 Jan 17 – Jan 24 Jan 24 – Jan 31
🧄 Garlic Fall: Nov 9 – Dec 7

Want this for all 50 crops, or as a printable seed-shelf schedule? Use the planting calendar and the seed starting scheduler — both can use Ajo's dates automatically after a lookup.

Reading the season in Ajo

With roughly 345 frost-free days, Ajo gardens fit long-season crops — melons, winter squash, sweet potatoes — with room left for spring and fall rounds of greens and roots. The first frost around Dec 21 is late enough that fall planting is a full second season, not an afterthought.

Frequently asked questions

When is the last frost in Ajo, AZ?

The average last spring frost in Ajo is around Jan 10, based on 1991–2020 climate normals. That's a median — about half of years see a later frost, so tender crops are safest going out a week or two after this date.

When is the first frost in Ajo, AZ?

The average first fall frost in Ajo arrives around Dec 21. Crops still in the garden need to mature before then, and frost-tender plants need harvesting or protection as the date approaches.

How long is the growing season in Ajo?

About 345 frost-free days on average, from Jan 10 to Dec 21. That comfortably fits long-season crops like melons and winter squash, plus spring and fall plantings of cool-season vegetables.

What USDA zone is Ajo in?

USDA zone 9b on the 2023 Plant Hardiness Zone Map. Note that zones describe winter cold, not frost timing — these frost dates are the numbers to plan plantings around.