Billings, Montana: planting zone & frost dates
Billings is in USDA plant hardiness zone 5a, where the average coldest winter night reaches -20 to -15°F (-28.9 to -26.1°C). The typical last spring frost is around May 11 and the first fall frost around Sep 28.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | May 21 | Sep 20 |
| Typical planning date (30% risk) | May 11 | Sep 28 |
| Median (50%) | May 5 | Oct 3 |
How to read this: after the spring "10% risk" date, a 32°F frost happens in only about 1 year in 10. In fall, the "10% risk" date is the early end — a frost before it happens about 1 year in 10.
Frost data comes from NOAA station BILLINGS WFO, MT (USC00240801), 2.8 mi (4.5 km) from the city center and 30 ft lower than the city center (-9 m). Record used for the 1991–2020 normals: 21 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Billings
All 4 ZIP codes covering Billings are in zone 5a.
Vegetable planting calendar for Billings
Dates are counted from the 30%-risk frost dates above (last frost May 11, first frost Sep 28). Shift a week later in cold spots or low-lying ground.
| Crop | Start indoors | Transplant / plant out | Direct sow | Fall crop sow/plant |
|---|---|---|---|---|
| Tomato | Mar 16 – Mar 30 | May 18 – Jun 1 | — | — |
| Pepper | Mar 2 – Mar 16 | May 25 – Jun 8 | — | — |
| Lettuce | Mar 30 – Apr 13 | Apr 27 – May 18 | Apr 13 – May 25 | Jul 20 – Aug 17 |
| Green Beans | — | — | May 18 – Jun 22 | Jul 6 – Jul 20 |
| Sweet Corn | — | — | May 18 – Jun 15 | — |
| Zucchini & Summer Squash | Apr 13 – Apr 20 | May 18 – Jun 1 | May 18 – Jun 8 | Jul 6 – Jul 20 |
| Cucumber | Apr 13 – Apr 20 | May 25 – Jun 1 | May 18 – Jun 8 | Jul 6 – Jul 20 |
| Carrot | — | — | Apr 20 – May 25 | Jul 6 – Jul 20 |
| Onion | Feb 16 – Mar 2 | Apr 13 – Apr 27 | — | — |
| Potato | — | Apr 13 – May 4 | — | — |
| Basil | Mar 30 – Apr 13 | May 25 – Jun 8 | May 25 – Jun 15 | — |
| Spinach | — | — | Mar 30 – Apr 27 | Aug 3 – Aug 31 |
| Kale | Mar 16 – Mar 30 | Apr 13 – May 4 | Apr 13 – May 4 | Jul 20 – Aug 17 |
| Broccoli | Mar 16 – Mar 30 | Apr 27 – May 18 | — | Jul 6 – Jul 20 |
| Peas | — | — | Mar 30 – Apr 20 | Jul 20 – Aug 3 |
| Eggplant | Mar 2 – Mar 16 | May 25 – Jun 8 | — | — |
| Cabbage | Mar 16 – Mar 30 | Apr 13 – Apr 27 | — | Jul 6 – Jul 20 |
| Radish | — | — | Apr 6 – May 25 | Aug 17 – Sep 14 |
| Strawberry | — | Apr 13 – May 4 | — | — |
| Beets | — | — | Apr 20 – Jun 1 | Jul 20 – Aug 3 |
Nearby cities in Montana
- Missoula — zone 5b, last frost May 22, first frost Sep 20
More: all Montana cities · other zone 5a cities: Minneapolis, MN, St. Paul, MN, Anchorage, AK, Sioux Falls, SD, Cedar Rapids, IA, Bloomington, MN, Sioux City, IA, Brooklyn Park, MN
Billings gardening questions
When is the last frost in Billings, MT?
Plan around May 11. At NOAA's Billings Wfo, MT station, 2.8 mi from the city center, there is a 30% chance of a 32°F frost after that date. Half of springs have their last frost by May 5, and after May 21 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Apr 23. The last frost is fairly predictable here: only 28 days separate the 90% and 10% dates (median for cities on this site: 36 days).
When should I plant tomatoes in Billings, MT?
Start seeds indoors Mar 16 – Mar 30 and set transplants outside May 18 – Jun 1, once nights stay above 50°F and the soil is near 60°F. That leaves 140 days between the 30% frost dates, enough for most varieties including 80–85-day slicers. More: tomato planting dates by zone.
How long is the growing season in Billings?
About 149 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 130 days, and in 1 year in 10 it runs 169 days or more. In fall there is a 10% chance of frost by Sep 20 and a 30% chance by Sep 28.
When should I plant a fall garden in Billings?
Count back from the first fall frost (Sep 28): transplant broccoli Jul 6 – Jul 20; sow kale Jul 20 – Aug 17; sow lettuce Jul 20 – Aug 17; sow radishes Aug 17 – Sep 14. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Oct 14. How the math works: succession and fall planting.
Did Billings's hardiness zone change on the 2023 map?
Yes. Most of Billings was zone 4b on the 2012 map and is zone 5a on the 2023 map — half a zone warmer, like about 56% of U.S. ZIP codes. The shift comes from a newer 1991–2020 averaging period plus more weather stations and better mapping; it does not mean last frost comes earlier. Why the 2023 map is warmer.