Castle Hot Springs, AZ Frost Dates & Growing Season

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

Last spring frost
Jan 15
~50% chance of frost after
First fall frost
Dec 22
~50% chance of frost before
Growing season
341 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 19 Jan 15 Feb 21
First fall frost Jan 26 Dec 22 Nov 29
Hard freeze (28°F), median last Jan 9 · first Jan 6

Computed from NOAA 1991–2020 climate normals at the CASTLE HOT SPRINGS 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 Castle Hot Springs

Computed from Castle Hot Springs'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 20 – Dec 4 Jan 22 – Jan 29
🫑 Peppers Nov 6 – Nov 20 Jan 29 – Feb 5
🥬 Lettuce Dec 4 – Dec 18 Dec 18 – Jan 1 Dec 18 – Jan 15
🫛 Peas Dec 4 – Dec 18
🥕 Carrots Dec 25 – Jan 15
🥦 Broccoli Nov 27 – Dec 11 Dec 25 – Jan 8
🥬 Kale Dec 4 – Dec 18 Dec 18 – Jan 1 Dec 18 – Jan 1
🥒 Cucumbers Dec 18 – Dec 25 Jan 22 – Jan 29 Jan 22 – Jan 29
🥒 Zucchini Dec 18 – Dec 25 Jan 22 – Jan 29 Jan 22 – Jan 29
🫘 Green Beans (Bush) Jan 22 – Jan 29
🌽 Sweet Corn Jan 22 – Jan 29
🌿 Basil Dec 4 – Dec 18 Jan 22 – Jan 29 Jan 29 – Feb 5
🧄 Garlic Fall: Nov 10 – Dec 8

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 Castle Hot Springs's dates automatically after a lookup.

Reading the season in Castle Hot Springs

With roughly 341 frost-free days, Castle Hot Springs 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 22 is late enough that fall planting is a full second season, not an afterthought.

Frequently asked questions

When is the last frost in Castle Hot Springs, AZ?

The average last spring frost in Castle Hot Springs is around Jan 15, 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 Castle Hot Springs, AZ?

The average first fall frost in Castle Hot Springs arrives around Dec 22. 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 Castle Hot Springs?

About 341 frost-free days on average, from Jan 15 to Dec 22. That comfortably fits long-season crops like melons and winter squash, plus spring and fall plantings of cool-season vegetables.

What USDA zone is Castle Hot Springs 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.