Busby, MT frost dates
Last spring frostMay 23median date
First fall frostSep 15median date
Growing season115 daysfrost-free
Hardiness zone5aZone 5a
How Busby compares
- In 8 years out of 10, the last spring frost in Busby falls between May 12 and June 7, a 26-day window. The first fall frost falls between September 1 and October 1.
- The median last frost is 4 days later than the Montana median of May 19.
- Its 115-day growing season is longer than 28% of the 325 Montana places with a regular frost season (state median 125 days).
- The last frost is 20 days later than the zone 5a median of May 3. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 5a chart.
- The weather station records an average of 193 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 12 |
| 50% (median) | May 23 |
| 10% (safe for tender plants) | June 7 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 1 |
| 50% (median) | September 15 |
| 90% (late) | October 1 |
Frost here means 32°F (0°C). A median date means half of years have their last frost earlier and half later.
Planting calendar for Busby, MT
Busby, MT frost dates — last frost May 23, first frost Sep 15, zone 5a. whenisthelastfrost.com
Crop
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Start indoors: Feb 28 to Mar 14Transplant outside: Apr 25 to May 9
Start indoors: Mar 14 to Mar 28Transplant outside: Jun 6 to Jun 20
Start indoors: Mar 14 to Mar 28Transplant outside: Jun 6 to Jun 20
Start indoors: Mar 28 to Apr 11Transplant outside: May 30 to Jun 13
Start indoors: Mar 28 to Apr 11Transplant outside: May 2 to May 16Sow outdoors: Apr 25 to May 30Plant for fall: Jul 21 to Aug 18
Start indoors: Mar 28 to Apr 11Transplant outside: Apr 25 to May 9Sow outdoors: Apr 25 to May 9Plant for fall: Jul 7 to Jul 28
Start indoors: Mar 28 to Apr 11Transplant outside: May 9 to May 23Plant for fall: Jun 9 to Jun 30
Start indoors: Mar 28 to Apr 11Transplant outside: May 2 to May 16Plant for fall: Jun 9 to Jun 30
Start indoors: Mar 28 to Apr 11Transplant outside: May 9 to May 23Plant for fall: Jun 9 to Jun 30
Start indoors: Apr 11 to Apr 25Transplant outside: Jun 13 to Jun 27Sow outdoors: Jun 13 to Jun 27
Start indoors: Apr 11 to Apr 25Transplant outside: May 30 to Jun 13
Sow outdoors: Apr 11 to May 2Plant for fall: Jun 23 to Jul 14
Sow outdoors: Apr 11 to May 2Plant for fall: Jul 21 to Aug 11
Sow outdoors: Apr 18 to May 30Plant for fall: Aug 4 to Aug 25
Start indoors: Apr 25 to May 2Transplant outside: Jun 6 to Jun 13Sow outdoors: May 30 to Jun 13Plant for fall: Jun 30 to Jul 14
Start indoors: Apr 25 to May 2Sow outdoors: May 30 to Jun 13Plant for fall: Jul 7 to Jul 21
Start indoors: Apr 25 to May 2Sow outdoors: May 30 to Jun 13
Start indoors: Apr 25 to May 2Transplant outside: Jun 6 to Jun 20
Sow outdoors: May 2 to May 30Plant for fall: Jun 23 to Jul 7
Sow outdoors: May 2 to May 30Plant for fall: Jul 7 to Jul 21
Sow outdoors: May 2 to May 23
Sow outdoors: May 9 to Jun 6Plant for fall: Jul 7 to Jul 21
Sow outdoors: May 9 to May 30Plant for fall: Jul 21 to Aug 11
Sow outdoors: May 30 to Jun 20
Sow outdoors: May 30 to Jun 13
Transplant outside: Jun 6 to Jun 27
Plant for fall: Sep 1 to Oct 6
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Busby, MT
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 28 – Mar 14 | Apr 25 – May 9 | — | — |
| Peppers | Mar 14 – Mar 28 | Jun 6 – Jun 20 | — | — |
| Eggplant | Mar 14 – Mar 28 | Jun 6 – Jun 20 | — | — |
| Tomatoes | Mar 28 – Apr 11 | May 30 – Jun 13 | — | — |
| Lettuce | Mar 28 – Apr 11 | May 2 – May 16 | Apr 25 – May 30 | Jul 21 – Aug 18 |
| Kale | Mar 28 – Apr 11 | Apr 25 – May 9 | Apr 25 – May 9 | Jul 7 – Jul 28 |
| Broccoli | Mar 28 – Apr 11 | May 9 – May 23 | — | Jun 9 – Jun 30 |
| Cabbage | Mar 28 – Apr 11 | May 2 – May 16 | — | Jun 9 – Jun 30 |
| Cauliflower | Mar 28 – Apr 11 | May 9 – May 23 | — | Jun 9 – Jun 30 |
| Okra | Apr 11 – Apr 25 | Jun 13 – Jun 27 | Jun 13 – Jun 27 | — |
| Basil | Apr 11 – Apr 25 | May 30 – Jun 13 | — | — |
| Peas | — | — | Apr 11 – May 2 | Jun 23 – Jul 14 |
| Spinach | — | — | Apr 11 – May 2 | Jul 21 – Aug 11 |
| Radishes | — | — | Apr 18 – May 30 | Aug 4 – Aug 25 |
| Cucumbers | Apr 25 – May 2 | Jun 6 – Jun 13 | May 30 – Jun 13 | Jun 30 – Jul 14 |
| Zucchini & Summer Squash | Apr 25 – May 2 | — | May 30 – Jun 13 | Jul 7 – Jul 21 |
| Winter Squash & Pumpkins | Apr 25 – May 2 | — | May 30 – Jun 13 | — |
| Melons & Watermelon | Apr 25 – May 2 | Jun 6 – Jun 20 | — | — |
| Carrots | — | — | May 2 – May 30 | Jun 23 – Jul 7 |
| Beets | — | — | May 2 – May 30 | Jul 7 – Jul 21 |
| Potatoes | — | — | May 2 – May 23 | — |
| Swiss Chard | — | — | May 9 – Jun 6 | Jul 7 – Jul 21 |
| Cilantro | — | — | May 9 – May 30 | Jul 21 – Aug 11 |
| Green Beans | — | — | May 30 – Jun 20 | — |
| Sweet Corn | — | — | May 30 – Jun 13 | — |
| Sweet Potatoes | — | Jun 6 – Jun 27 | — | — |
| Garlic | — | — | — | Sep 1 – Oct 6 |
Dates come from the median frost dates and common extension-service timing. Adjust for your soil temperature, microclimate and the varieties you grow.
About these dates
Based on 1991–2020 NOAA climate normals for the Busby, MT weather station, 7 km away (elevation 3,432 ft (1,046 m)).
Frost dates near Busby
- Lame Deer May 23 · Sep 15
- Birney May 23 · Sep 15
- Decker May 18 · Sep 24
- Colstrip May 15 · Sep 30
- Ashland May 18 · Sep 22
- Lodge Grass May 21 · Sep 17
- Garryowen May 13 · Sep 29
- Crow Agency May 13 · Sep 29
- Bighorn May 26 · Sep 16
- Hardin May 13 · Sep 29
Frequently asked questions
When is the last frost in Busby, MT?
The median last spring frost in Busby, MT is May 23. There is still about a 10% chance of frost after June 7, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Busby, MT?
The median first fall frost is September 15, with about a 10% chance of frost before September 1.
How long is the growing season in Busby, MT?
About 115 days between the median last spring frost and first fall frost.
What planting zone is Busby, MT?
Busby, MT is in USDA hardiness zone 5a.