Phoenix, AZ Frost Dates: Last Spring and First Fall Frost

The last spring frost in Phoenix, AZ comes on January 8 in a typical year, and the first fall frost follows on December 25, leaving a frost-free season of 354 days.

Because half of all years do worse than the typical date, the dates that matter for tender plants are the late spring date, February 12, and the early fall date, December 5, each of which one year in ten fails to beat. Compared with the 100-city median of 229 days, Phoenix gets 125 days extra before frost returns.

These dates come from the NOAA weather station Phoenix Deer Valley Muni AP (ID USW00003184), 8.0 miles north of the Census Bureau's internal point for Phoenix, at about 1,450 feet above sea level.

Phoenix's last spring frost, by chance

NOAA gives December 16 as the date a winter freeze is still ahead in nine years out of ten, January 8 as the date it is still ahead in half of them, and February 12 as the date only one year in ten passes.

A span of 58 days from the 90% date to the 10% date is wide for these pages. Spring in Phoenix is less predictable than in most of the 100 cities, and the late date is 35 days past the typical one.

Phoenix's first fall frost, by chance

NOAA's early fall date for Phoenix is December 5, its even-odds date is December 25 and its late date is January 23; the first freeze has come by each of them in one, five and nine years out of ten.

49 days separate the early and late fall dates, a broad band compared with most cities here, so a fall crop in Phoenix should be planned against the early date, not the typical one.

How long is the frost-free season in Phoenix?

Phoenix has far more frost-free days than the middle of these pages, and slow crops benefit most, as the planting dates below show. The gap between a typical year and a short one is 34 days, wider than for most cities on these pages. Count on 320 days, not 354 days, when a crop has little slack.

The season lengths come from NOAA's simulated years, not from subtracting one typical date from the other, so the two will not match to the day. A night at or below 32°F shows up in only 70.2% of years here. In the remaining 29.8% winter passes without one, so these dates describe when frost is possible, not when it is certain.

28°F dates in Phoenix

The two freezes sit close together here. The typical hard freeze reaches Phoenix on January 7, 13 days after the first frost, and ends on January 8, 0 days ahead of the last. One spring in ten still has a 28°F night on or after February 2, and one fall in ten sees the first by December 14.

Planting dates for Phoenix, counted from the frost dates

University of New Hampshire Extension sorts vegetables by how they cope with cold. Cool-season crops go out before the last frost: counting from January 8, cabbage transplants go in on December 11 and lettuce from December 11 to December 18. Tender crops wait until it has passed, with peppers going out on January 22 and beans sown on or after January 8. Peas have no frost-based date in the University of New Hampshire Extension sheet: they go in as soon as the soil thaws.

Counting from the late date instead of the typical one adds 35 days before tender crops go out, a big difference in Phoenix. Gardeners who cannot cover plants on a cold night should take the later date.

For fall, NC State Extension gives each crop's days to harvest, and University of Georgia Extension adds a harvest allowance of 18 days; you count back that total from the first frost. Every one of the 34 fall crops in the fall planner still has a last planting day on or after July in Phoenix. The slowest crop that still fits is parsnips, which needs 148 days before the early first frost and so must be in by July 10.

Worked example: the last day for fall broccoli in Phoenix

Take fall broccoli in Phoenix. NC State Extension lists up to 80 days from transplant to harvest, and University of Georgia Extension adds a harvest allowance of 18 days, so the plants need 98 days before the first frost. Counting back from the typical first frost, December 25, the last planting day is September 18. Counting back from the early date, December 5, it is August 29.

That is 20 days between the typical and the early schedule; broccoli planted on the later of them risks a frost before harvest in one fall out of ten.

The same crop family has a spring clock too. University of New Hampshire Extension sets cabbage out ahead of the last frost, and from January 8 in Phoenix that means on December 11.

Where Phoenix's numbers are measured

The station is 8.0 miles north of the Census Bureau's internal point for Phoenix, several miles out, so look at the nearest-station list in the frost dates tool before you rely on it.

At about 1,450 feet, it ranks above 82 and below 17 of the 100 stations used for these pages. Its completeness flag is R, which NOAA uses for a representative record.

No elevation is available for Phoenix in the Census data we saved, so the station's height may or may not match your garden's. Compare nearby stations in the frost dates tool if it does not, and err toward the colder dates.

Nearby cities and their frost dates

Three cities on these pages lie within a hundred miles of Phoenix, the nearest Glendale, AZ at 6.3 miles, which makes the comparison below a close one.

• Glendale, AZ, 6.3 miles to the south-west: last frost January 20, first frost December 15, 331 days frost-free; its last frost comes 12 days after Phoenix's, and it has 23 days less without frost.
• Scottsdale, AZ, 15 miles to the north-east: last frost January 27, first frost December 21, 330 days frost-free; the last frost is 19 days later than in Phoenix, and the season runs 24 days shorter.
• Chandler, AZ, 24 miles to the south-east: last frost February 13, first frost December 5, 298 days frost-free; the last frost is 36 days later than in Phoenix, and it has 56 days less without frost.

Next steps for Phoenix gardeners

Start with the spring planting planner for the whole crop list counted from these dates, and the fall planting planner for the last planting days. The frost dates tool shows every level of risk at this station, and the hardiness zone lookup covers winter survival for shrubs and perennials.

Every city covered is on the city frost dates index, sorted by state.

Where these numbers come from

Every frost and freeze date comes from the station's entry in NOAA's U.S. Climate Normals for 1991–2020 (doi:10.25921/4ek7-fk11), with no adjustment, and NOAA's documentation explains what each probability means. Phoenix and its internal point are listed in the Census Bureau's 2024 Gazetteer of places; its place in the ranking comes from the Vintage 2024 population estimates, which count 1,673,164 residents.

Planting dates here are those rules from University of New Hampshire Extension, NC State Extension and University of Georgia Extension, applied to this station's frost dates and nothing else. The methodology page explains how each figure is checked.

These dates describe odds over many years, not next week's weather. Look at the forecast before you plant, and keep a sheet or row cover ready for a night that does not follow the odds.