Frost dates for Billings, Montana
In Billings, half of springs have had their last frost by May 5 (and 1 spring in 10 still has one after May 21), and half of falls have had their first frost by October 3, leaving about 149 frost-free days in a typical year. Here is how sure those dates are, what they mean for planting, and where they come from.
Frost dates for
Billings, Montana
Last spring frost
May 5
Half of springs have their last frost by this date. For a safer bet, wait until May 21: only 1 spring in 10 has a frost after that.
First fall frost
October 3
Half of falls have their first frost by this date. In 1 fall in 10 it comes by September 20.
Growing season
149 days
Frost-free days in a typical year. 9 years in 10 get at least 130.
Hardiness zone
5a
2023 USDA map: the coldest night of winter averages −20°F to −15°F. On the 2012 map it was 4b, half a zone colder. All 2 ZIP codes within about 6 miles of the city's center are in zone 5a.
Print a year planner for Billings
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 | April 23 | May 5 | May 21 |
| First frost in fall | September 20 | October 3 | October 17 |
The frost-free season between them runs 149 days in a typical year. In 1 year in 10 it is 169 days or longer, and in 1 year in 10 it is 130 days or shorter.
- Hard freeze (28°F): typically last on April 23 and first on October 14. 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 May 19 and first on September 23. 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.
In 8 springs out of 10, the last frost in Billings comes between April 23 and May 21, a window of 28 days. That is about average for NOAA's stations (the typical window is 31 days).
Among Montana's 216 NOAA stations with a frost every year, 97 percent have their typical last frost later than Billings does.
Planting calendar for Billings
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.
Your season is too short for a separate fall planting of cabbage: sown late enough to be a fall crop, it wouldn't be ready before the typical first frost. Your spring planting is your harvest.
| When | What to do | Why then |
|---|---|---|
| February | ||
| February 17 to March 17 | Broccoli and cabbage Start seeds indoors | 5 to 7 weeks before planting them out |
| March | ||
| March 3 to 31 | Cauliflower Start seeds indoors | 5 to 7 weeks before planting out |
| March 17 to April 7 | Eggplant Start seeds indoors | 6 to 9 weeks before planting out |
| March 24 to April 7 | Peppers Start seeds indoors | 6 to 8 weeks before planting out |
| March 31 to April 14 | Tomatoes Start seeds indoors | 5 to 7 weeks before planting out |
| April | ||
| April 7 to 21 | Peas, spinach, lettuce, radishes, onion sets, turnips Sow outdoors, as early as | hardy crops: 2 to 4 weeks before the typical last frost |
| April 7 to 21 | Broccoli and cabbage Plant out, as early as | hardy crops: 2 to 4 weeks before the typical last frost |
| April 21 to May 5 | Beets, carrots, potatoes, Swiss chard Plant outdoors, as early as | semi-hardy crops: up to 2 weeks before the typical last frost |
| April 21 to May 5 | Cauliflower Plant out, as early as | semi-hardy: up to 2 weeks before the typical last frost |
| May | ||
| May 5 | Snap beans, sweet corn, cucumbers, summer squash Sow outdoors around | tender crops: around the typical last frost date |
| May 19 | Tomatoes, peppers, eggplant Plant out from | very tender: 2 weeks or more after the typical last frost |
| May 19 | Melons, winter squash, pumpkins, lima beans Sow outdoors from | very tender: 2 weeks or more after the typical last frost |
| May 28 to June 11 | Broccoli for fall Start seeds | set the plants out by July 16 |
| July | ||
| July 7 | 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 |
| July 11 | Carrots for fall Last date to sow | 70 days to harvest, plus 2 weeks for slower fall growth |
| July 12 | 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 |
| July 16 | Peas for fall Last date to sow | 65 days to harvest, plus 2 weeks for slower fall growth |
| July 17 | 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 |
| July 21 | Leaf lettuce and beets for fall Last date to sow | 60 days to harvest, plus 2 weeks for slower fall growth |
| July 31 | Turnips and kohlrabi for fall Last date to sow | 50 days to harvest, plus 2 weeks for slower fall growth |
| August | ||
| August 10 | Spinach for fall Last date to sow | 40 days to harvest, plus 2 weeks for slower fall growth |
| August 20 | Radishes for fall Last date to sow | 30 days to harvest, plus 2 weeks for slower fall growth |
| September | ||
| September 20 | 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 |
| October | ||
| October 21 to 28 | Garlic Plant cloves | one or two weeks after the typical first hard freeze (28°F), our reading of the first killing frost |
Want more insurance? Shift every spring date 16 days later. That plans around May 21, 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 Billings WFO (station USC00240801), 3 miles from the center of Billings. It sits at about the same elevation, 3,190 feet above sea level. NOAA rates this station's record as representative: at least 10 of the 30 years, with the gaps filled from nearby stations.
Our ZIP code lookup matches these 3 ZIP codes to the same station, so they get the same dates: 59044, 59102, 59106. Hardiness zones are worked out separately for each ZIP code.
See frost dates across Montana, or look up your own ZIP code for the station nearest you. Want the background? Read what a last frost date really means.