Tucson, Arizona Frost Dates, Growing Season & Hardiness Zone

When is the last frost in Tucson?

Some winters here pass without a single 32°F night: NOAA's yearly chance at Tucson International Airport is 98.9%. The dates on this page cover only the years that do freeze, which is how NOAA computes them (conditional probabilities).

Counting only years with a freeze, half are past their last 32°F night by Feb 5, and 1 in 10 has one after Mar 2. NOAA puts the yearly chance of a 36°F night (frost possible on plants) at 100%, with the last one typically around Feb 28. The yearly chance of a 28°F hard freeze is 69.6%.

Frost risk in Tucson drags on well past the typical date. The safer 1-in-10 date (Mar 2) is 25 days later than the typical Feb 5, so protect tender plants set out early on cold nights.

Cool nights hang on after the last freeze. In years with a freeze, the typical last 32°F night is around Feb 5, and the typical last 36°F night (frost possible on plants in low spots) comes 23 days later, around Feb 28. On clear, calm nights, frost can form on leaves while the thermometer still reads above freezing.

Is it too early to plant in Tucson?

Before Feb 5 the odds of another 32°F night are better than even; after Mar 2 they are about 1 in 10 or less.

Today's risk is computed in your browser from the same NOAA probability table, shown as the range between the two nearest NOAA probability levels.

When is the first frost in Tucson?

Counting only years with a freeze, the first 32°F night comes by Dec 9 in half of them and as early as Nov 21 in 1 in 10. The first 36°F night (frost possible on plants) typically comes around Nov 26. NOAA puts the yearly chance of a 28°F hard freeze at 69.6%.

To time a fall crop, count back from the typical first frost (Dec 9) or the safer Nov 21. The planting calendar works it out crop by crop.

How long is Tucson's growing season?

A typical year in Tucson has 307 days between the last spring and first fall 32°F nights. In about 1 year in 10, there are fewer than 274 days.

This much frost-free time means many crops can go in twice, in spring and again for a fall harvest.

The station averages 7,673 growing degree days (base 50°F) a year. That number measures how much heat crops have to grow on.

How does Tucson's season compare?

Among the 3 Arizona cities with frost dates on this site, the typical frost-free season in Tucson (307 days) is the shortest.

Compared with the 56 U.S. cities with frost dates on this site, this typical frost-free season is longer than in 47 and shorter than in 8.

Growing degree days (base 50°F)

Annual normal: 7,673 GDD (NOAA flag S, 28 years). Running total by the end of each month (sum of NOAA daily GDD normals, so the year-end total can differ slightly from the annual normal):

What growing zone is Tucson? (USDA 2023)

The 2023 USDA map puts Tucson in zone 9a–9b (20 to 30°F average coldest winter night). On the 2012 map, most of the city was 9a. Comparing ZIPs listed in both tables, 11 of 29 moved up half a zone.

Zones: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed 2026-10-08. Shown as published in the ZIP tables; this page does not show a zone map. Not the official USDA Plant Hardiness Zone Map (official map: planthardiness.ars.usda.gov).

Does the new zone change Tucson's frost dates?

No. A hardiness zone reflects only the average coldest winter temperature, not the timing of spring or fall frost. Tucson's frost dates come from NOAA's 1991–2020 frost probabilities, and the 2023 zone map didn't change them. Pick perennials that survive winter by zone; time your planting by frost dates.

Why do Tucson frost dates differ between websites?

If you've seen Feb 17 listed as Tucson's last frost date, that's the 30%-risk date: in years with a freeze, about 3 in 10 still get a 32°F night after it. We lead with Feb 5, the 50% (median) date.

We call Mar 2 the 'safer' date. It's the 10%-risk date: in about 1 in 10 years with a freeze, a 32°F night still comes after it.

Feb 28 is the 50% date for a 36°F night (frost possible on plants), not a 32°F freeze. Sites that treat 36°F as the danger line show later dates.

The choice of weather station matters too. The 8 stations within 25 miles of the city center that pass our quality rules give typical (50%) last 32°F frost dates from Jan 20 to Apr 2; see the table below.

Which weather station is this based on?

Station

Tucson International Airport (NOAA USW00023160, WBAN/ASOS-AWOS)

Distance

5.2 mi WSW of the city center

Elevation

2,549 ft; city center 2,698 ft (USGS), difference −149 ft

Record

NOAA completeness flag S, 29 of 30 years (1991–2020)

Confidence

High (rule)

Confidence: High. The station is close (5.2 miles from the city center), its elevation differs by just 149 ft, and its frost statistics meet our completeness rule (NOAA flag S, 29 of 30 years).

Tucson planting dates at a glance

Balanced dates use the 30%-risk last-frost date as the anchor. The Tucson planting calendar has typical and safe dates, fall planting and a month-by-month list for 26 vegetables.

When to plant tomatoes in Tucson · Fall planting dates for Tucson

Frost dates near Tucson

All Arizona cities

Frequently asked questions

What is the average last frost date in Tucson?

Not every winter in Tucson freezes: NOAA puts the yearly chance of a 32°F night at Tucson International Airport at 98.9%. In the years that do freeze, the typical (50%) last one is Feb 5, and only about 1 in 10 of those years has one after Mar 2.

When is the first frost in Tucson?

In years with a freeze, the first 32°F night typically arrives by Dec 9, and in about 1 in 10 of those years it comes as early as Nov 21. NOAA puts the yearly chance of a 32°F night at Tucson International Airport at 98.9%.

What growing zone is Tucson, Arizona?

Tucson is in USDA hardiness zone 9a–9b on the 2023 map. Most of the city was already 9a on the 2012 map, though 11 of 29 city ZIPs changed zone.

Is it too early to plant in Tucson?

For frost-tender plants, wait until at least Feb 5. Not every year freezes here: NOAA puts the yearly chance of a 32°F night at Tucson International Airport at 98.9%. In years that do, another 32°F night after Feb 5 happens about half the time, and after Mar 2 about 1 time in 10. Cool-season crops like peas and lettuce can go in weeks earlier; the planting calendar has the dates.

What temperature is a killing frost?

A light frost is enough to kill tender crops such as tomatoes. CSU Extension describes 28–32°F as a light frost and anything below 28°F as a heavy frost. We report NOAA odds at three thresholds: 36°F (frost possible on plants), 32°F (freeze, our headline) and 28°F (hard freeze).

Is first frost the same as first freeze?

Not exactly. A freeze is about the air reaching 32°F. Frost is ice on surfaces, which can form on calm, clear nights while the air is still a few degrees above freezing. The first 36°F night (frost possible on plants) in Tucson typically comes around Nov 26. Freezes don't come every year here: NOAA puts the yearly chance of a 32°F night at 98.9%, and in years that have one, the first typically arrives around Dec 9.

Download & sources

• Add Tucson frost & planting dates to your calendar (.ics, 2027)
• Printable planting calendar (PDF)
• How these numbers are calculated

Data: NOAA NCEI U.S. Climate Normals 1991–2020 (annual/seasonal and daily normals, station USW00023160); USDA Plant Hardiness Zone ZIP tables 2023 and 2012 by the PRISM Group, Oregon State University; Census 2020 ZIP/place relationship file; USGS elevation. Long-term odds, not a forecast. Figures and sentences are generated from these data by fixed rules; see the methodology. Last updated 2026-10-08.