Phoenix, AZ Frost Dates
Published: February 1, 2026 · Updated: April 23, 2026
USDA Zone 9b
Last Spring Frost
January 15
Safe to transplant after this date
First Fall Frost
December 31
Protect tender plants before this date
Frost-Free Season
350 days
Year-round to Year-round
230 days until last frost in Phoenix — January 15
Phoenix’s zone 9b climate means frost is a minor consideration. Essentially frost-free. Lawns grow year-round. Southern California, Southern Arizona, South Florida. Rather than a single planting season, Phoenix gardeners work almost year-round.
Complete Planting Calendar for Phoenix
Lawn Care Timing for Phoenix
Based on Phoenix's USDA zone 9b frost dates: The last frost of January 15 marks when warm-season grasses begin recovering. Apply spring fertilizer in February when soil reaches 55°F. The first fall frost of December 31 sets your deadlines — complete overseeding by October–November and apply winterizer by Not needed.
USDA Zone 9b Summary
Essentially frost-free. Lawns grow year-round. Southern California, Southern Arizona, South Florida.
Frequently Asked Questions
What is the last frost date in Phoenix, AZ?
The average last spring frost in Phoenix is January 15. This is based on USDA zone 9b historical averages. Plan transplanting and spring lawn care around this date — wait 2 weeks after for frost-sensitive plantings.
When is the first fall frost in Phoenix?
Phoenix’s average first fall frost is December 31. This sets deadlines for fall overseeding (must be done when temperatures cool) and winterizer application (by Not needed).
When should I plant tomatoes in Phoenix?
Transplant tomato seedlings outdoors after January 15. Start seeds indoors Year-round. Direct sow warm-season crops february–april.
When should I overseed my lawn in Phoenix?
The prime overseeding window in Phoenix is October–November. This ensures warm soil for germination before the first fall frost on December 31.
When should I apply winterizer in Phoenix?
Apply winterizer fertilizer in Phoenix by Not needed. This high-potassium application hardens grass cell walls before freeze damage. Your first fall frost of December 31 is the hard deadline.