Frost dates for Tucson, Arizona
Tucson doesn't get a freezing night every winter: about 99 years in 100 have one. In those years, half have had their last frost by February 5 and half their first by December 9.
Frost dates for
Tucson, Arizona
Last spring frost
February 5
Not every winter has one: about 99 years in 100 have a freezing night here. In those years, half have their last frost by this date, and 1 in 10 still have one after March 2.
First fall frost
December 9
In years with a freeze, half have their first one by this date, and 1 in 10 by November 21.
Growing season
307 days
Frost-free days in a typical year. 9 years in 10 get at least 274.
Hardiness zone
9b
2023 USDA map: the coldest night of winter averages 25°F to 30°F. On the 2012 map it was 9a, half a zone colder. ZIP codes within about 6 miles of the city's center: 2 in 9a and 8 in 9b.
Stations near you disagree. NOAA's Tucson International Airport (5 miles away, at 2,550 feet above sea level), the one we used, gives a typical last frost of February 5 and a typical first frost of December 9. NOAA's Tucson WFO (7 miles away, at 2,430 feet above sea level) gives a typical last frost of January 20 and a typical first frost of December 17. So the typical last frost could fall anywhere from January 20 to February 5 and the typical first frost from December 9 to 17, depending on whether your garden is more like one or the other. Local terrain matters: hillsides, valley floors, water and city heat can change frost dates a lot over a few miles. Treat the dates here as a starting point, and compare with a nearby gardener or your county extension office.
Print a year planner for Tucson
Frost risk through the year
How sure are these dates?
A frost date is a probability, not a promise. NOAA worked out, from 30 years of nightly lows, how often the last spring frost and the first fall frost fall on each date. The middle column is the typical year. The outer columns are the early and late years that come about once a decade.
| Early year 1 in 10 | Typical year 1 in 2 | Late year 1 in 10 | |
|---|---|---|---|
| Last frost in spring | January 4 | February 5 | March 2 |
| First frost in fall | November 21 | December 9 | January 3 |
The frost-free season between them runs 307 days in a typical year. In 1 year in 10 it is 344 days or longer, and in 1 year in 10 it is 274 days or shorter.
- Hard freeze (28°F): about 70 years in 100 have one. In those years the last typically comes on January 11 and the first on December 26. It is a harder freeze than the 32°F frost line, cold enough to damage many garden plants; how hardy a crop is decides whether it comes through. (The National Weather Service's own hard-freeze threshold varies from office to office.)
- Frost possible (36°F at the station): typically last on February 28 and first on November 26. On clear, still nights the ground can be several degrees colder than the thermometer, so frost can form on plants when the official reading is in the mid-30s.
Planting calendar for Tucson
These dates count from the typical last and first frosts, using the planting rules published by Colorado State University Extension (spring), Virginia Cooperative Extension (fall crops) and University of Minnesota Extension (garlic, where winters are hard). Weather in any one year can run early or late, so check the forecast before you plant tender crops.
Frost doesn't come every year here: about 99 years in 100 have at least one freezing night. The calendar is built on the dates for the years that do.
We don't give a garlic date here. The rule we use, from the University of Minnesota Extension, counts from the first killing frost, and it works where a hard freeze comes every year before the ground freezes. Your county's extension office can tell you when to plant garlic in your climate.
Your typical last frost comes before mid-February. Where winters are this mild, summer heat limits the garden as much as frost does, and most planting happens in fall and late winter. Your county's extension office publishes a calendar made for your climate.
| When | What to do | Why then |
|---|---|---|
| January | ||
| January 1 to 15 | Tomatoes Start seeds indoors | 5 to 7 weeks before planting out |
| January 8 to 22 | Peas, spinach, lettuce, radishes, onion sets, turnips Sow outdoors, as early as | hardy crops: 2 to 4 weeks before the typical last frost |
| January 8 to 22 | Broccoli and cabbage Plant out, as early as | hardy crops: 2 to 4 weeks before the typical last frost |
| January 22 to February 5 | Beets, carrots, potatoes, Swiss chard Plant outdoors, as early as | semi-hardy crops: up to 2 weeks before the typical last frost |
| January 22 to February 5 | Cauliflower Plant out, as early as | semi-hardy: up to 2 weeks before the typical last frost |
| February | ||
| February 5 | Snap beans, sweet corn, cucumbers, summer squash Sow outdoors around | tender crops: around the typical last frost date |
| February 19 | Tomatoes, peppers, eggplant Plant out from | very tender: 2 weeks or more after the typical last frost |
| February 19 | Melons, winter squash, pumpkins, lima beans Sow outdoors from | very tender: 2 weeks or more after the typical last frost |
| July | ||
| July 14 to 28 | Cabbage for fall Start seeds | set the plants out by September 1 |
| August | ||
| August 3 to 17 | Broccoli for fall Start seeds | set the plants out by September 21 |
| September | ||
| September 12 | Snap beans for fall Last date to sow | 60 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| September 16 | Carrots for fall Last date to sow | 70 days to harvest, plus 2 weeks for slower fall growth |
| September 17 | Cucumbers for fall Last date to sow | 55 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| September 21 | Peas for fall Last date to sow | 65 days to harvest, plus 2 weeks for slower fall growth |
| September 22 | Summer squash for fall Last date to sow | 50 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| September 26 | Leaf lettuce and beets for fall Last date to sow | 60 days to harvest, plus 2 weeks for slower fall growth |
| October | ||
| October 6 | Turnips and kohlrabi for fall Last date to sow | 50 days to harvest, plus 2 weeks for slower fall growth |
| October 16 | Spinach for fall Last date to sow | 40 days to harvest, plus 2 weeks for slower fall growth |
| October 26 | Radishes for fall Last date to sow | 30 days to harvest, plus 2 weeks for slower fall growth |
| November | ||
| November 20 to December 18 | Broccoli and cabbage Start seeds indoors | 5 to 7 weeks before planting them out |
| November 21 | Tomatoes, peppers, squash, melons, cucumbers Watch the forecast from | in 1 fall in 10 the first frost comes by this date; pick tender crops before a frost |
| December | ||
| December 4 to January 1 | Cauliflower Start seeds indoors | 5 to 7 weeks before planting out |
| December 18 to January 8 | Eggplant Start seeds indoors | 6 to 9 weeks before planting out |
| December 25 to January 8 | Peppers Start seeds indoors | 6 to 8 weeks before planting out |
Want more insurance? Shift every spring date 25 days later. That plans around March 2, the date after which only 1 spring in 10 has a frost.
For spring bulbs such as tulips and daffodils, plant once the soil has cooled to about 50 to 55°F and keep going until a couple of weeks before the ground freezes. Our guide to fall planting explains how to tell.
Where these numbers come from
These dates come from NOAA's weather station Tucson International Airport (station USW00023160), 5 miles from the center of Tucson. It sits 140 feet lower, at 2,550 feet above sea level. NOAA rates this station's record as standard: at least 24 of the 30 years, with gaps filled from nearby stations.
Our ZIP code lookup matches these 10 ZIP codes to the same station, so they get the same dates: 85706, 85707, 85708, 85709, 85710, 85711, 85714, 85734, 85756, 85757. Hardiness zones are worked out separately for each ZIP code.
The nearest other places with pages
- Gilbert, Arizona: frost not every year (95 miles away)
- Chandler, Arizona: frost not every year (95 miles away)
- Mesa, Arizona: frost not every year (100 miles away)
See frost dates across Arizona, or look up your own ZIP code for the station nearest you. Want the background? Read what a last frost date really means.