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

Tucson gardeners can count on February 5 as the even-odds date for the last spring frost and December 9 as the even-odds date for the first fall frost, which adds up to 307 days without a freeze in a typical year.

Because half of all years do worse than the typical date, the dates that matter for tender plants are the late spring date, March 2, and the early fall date, November 21, each of which one year in ten fails to beat. Tucson's season is 78 days longer than the 229 days median across the 100 cities on these pages, which puts it 21st for season length.

These dates come from the NOAA weather station Tucson International AP (ID USW00023160), 5.2 miles west of the Census Bureau's internal point for Tucson, at about 2,550 feet above sea level.

Tucson's last spring frost, by chance

NOAA gives January 4 as the date a spring freeze is still ahead in nine years out of ten, February 5 as the date it is still ahead in half of them, and March 2 as the date only one year in ten passes.

The earliest and latest of these dates are 57 days apart, wider than for most of the 100 cities here. A freeze can still come 25 days after the typical date in Tucson, which is why the late date matters more here than in most places.

Tucson's first fall frost, by chance

In Tucson the first freeze has arrived by November 21 in one fall out of ten, by December 9 in five, and by January 3 in nine.

The fall dates spread over 43 days, wider than for most cities on these pages. One year in ten brings the first freeze 18 days ahead of the typical date.

Tucson's frost-free season

Tucson has far more frost-free days than the middle of these pages, and slow crops benefit most, as the planting dates below show. Season length swings more here than in most of the 100 cities: 307 days in a typical year, 274 days in a short one, a difference of 33 days.

NOAA counts these days from its own simulations, so they will not equal the number of days between the two typical dates exactly. At Tucson International AP, 98.9% of years have a night at or below 32°F. In the rest there is no last or first frost to date.

Hard freeze dates for Tucson

Hard freezes are late to arrive in Tucson and early to leave: December 26 in fall, 17 days behind the first frost, and January 11 in spring, 25 days ahead of the last. The late 28°F spring date, February 17, is the one that still catches blooms and young transplants one year in ten, and the early fall date, November 30, is when a hard freeze has arrived in one fall out of ten.

What this means for planting in Tucson

Counting from February 5, University of New Hampshire Extension puts cabbage transplants out on January 8 and lettuce from January 8 to January 15, ahead of the last frost, and holds peppers until February 19 and beans until February 5 or later. Peas have no frost-based date in the University of New Hampshire Extension sheet: they go in as soon as the soil thaws.

The late date, March 2, falls 25 days after the typical one, so counting from it pushes every tender crop back by more than three weeks. In Tucson that is a real choice between earlier planting with cover on hand and later planting with none.

Tucson's first frost leaves room for only 33 of the 34 fall crops, counting back NC State Extension's days to harvest and University of Georgia Extension's harvest allowance of 18 days; for the other 1 the last planting day falls before July. Of the crops that fit, bulb onions is the slowest: 138 days from planting to the early frost, which makes July 6 its last day.

Worked example: the last day for fall broccoli in Tucson

Work through broccoli transplants for fall in Tucson. The longest days to harvest NC State Extension gives is 80 days, plus University of Georgia Extension's allowance of 18 days, for 98 days in all. Subtract that from the typical first frost on December 9 and the last day to plant is September 2; subtract it from the early date on November 21 and it is August 15.

That is 18 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 February 5 in Tucson that means on January 8.

Where Tucson's numbers are measured

The nearest usable station stands 5.2 miles west of Tucson's internal point, near the city but not in it.

At about 2,550 feet, it ranks above 88 and below 11 of the 100 stations used for these pages. NOAA flags this station's record as standard, the code S, for the data behind its 50% last-frost value.

The Census Gazetteer gives no elevation for Tucson itself, so this page cannot tell you whether your garden sits above or below the station. If it is noticeably higher or lower, compare the stations the frost dates tool lists nearby and lean toward the colder reading.

Tucson compared with nearby cities

Three cities on these pages lie within a hundred miles of Tucson, the nearest Gilbert, AZ at 95 miles, which makes the comparison below a close one. Note that the Gilbert station stands 1,150 feet lower than Tucson's.

• Gilbert, AZ, 95 miles to the north-west: last frost February 1, first frost December 11, 315 days frost-free; spring frost ends 4 days sooner than in Tucson, and it has 8 days more without frost.
• Chandler, AZ lies 97 miles north-west of Tucson. Typical last frost February 13, first frost December 5, 298 days between; the last frost is 8 days later than in Tucson, and the season runs 9 days shorter.
• Mesa, AZ, 99 miles to the north-west: last frost February 1, first frost December 10, 312 days frost-free; spring frost ends 4 days sooner than in Tucson, and frost-free days differ from Tucson's by less than a week.

Take these dates further

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

The frost and freeze dates are NOAA's U.S. Climate Normals for 1991–2020 (doi:10.25921/4ek7-fk11), copied from the station's own record without adjustment; NOAA's documentation defines each probability. The Census Bureau's 2024 Gazetteer places Tucson on the map, and its Vintage 2024 estimates, 554,013 people here, decide which cities get a page.

University of New Hampshire Extension, NC State Extension and University of Georgia Extension supply the planting rules; this page only counts them from the station's dates. 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.