Glasgow, MT frost dates
Last spring frostMay 6median date
First fall frostSep 30median date
Growing season147 daysfrost-free
Hardiness zone4aZone 4a
How Glasgow compares
- In 8 years out of 10, the last spring frost in Glasgow falls between April 24 and May 18, a 24-day window. The first fall frost falls between September 17 and October 13.
- The median last frost is 13 days earlier than the Montana median of May 19.
- Its 147-day growing season is longer than 92% of the 325 Montana places with a regular frost season (state median 125 days).
- The last frost is 6 days earlier than the zone 4a median of May 12. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 4a chart.
- The weather station records an average of 181 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 24 |
| 50% (median) | May 6 |
| 10% (safe for tender plants) | May 18 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 17 |
| 50% (median) | September 30 |
| 90% (late) | October 13 |
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 Glasgow, MT
Glasgow, MT frost dates — last frost May 6, first frost Sep 30, zone 4a. whenisthelastfrost.com
Crop
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Start indoors: Feb 11 to Feb 25Transplant outside: Apr 8 to Apr 22
Start indoors: Feb 25 to Mar 11Transplant outside: May 20 to Jun 3
Start indoors: Feb 25 to Mar 11Transplant outside: May 20 to Jun 3
Start indoors: Mar 11 to Mar 25Transplant outside: May 13 to May 27
Start indoors: Mar 11 to Mar 25Transplant outside: Apr 15 to Apr 29Sow outdoors: Apr 8 to May 13Plant for fall: Aug 5 to Sep 2
Start indoors: Mar 11 to Mar 25Transplant outside: Apr 8 to Apr 22Sow outdoors: Apr 8 to Apr 22Plant for fall: Jul 22 to Aug 12
Start indoors: Mar 11 to Mar 25Transplant outside: Apr 22 to May 6Plant for fall: Jun 24 to Jul 15
Start indoors: Mar 11 to Mar 25Transplant outside: Apr 15 to Apr 29Plant for fall: Jun 24 to Jul 15
Start indoors: Mar 11 to Mar 25Transplant outside: Apr 22 to May 6Plant for fall: Jun 24 to Jul 15
Start indoors: Mar 25 to Apr 8Transplant outside: May 27 to Jun 10Sow outdoors: May 27 to Jun 10
Start indoors: Mar 25 to Apr 8Transplant outside: May 13 to May 27
Sow outdoors: Mar 25 to Apr 15Plant for fall: Jul 8 to Jul 29
Sow outdoors: Mar 25 to Apr 15Plant for fall: Aug 5 to Aug 26
Sow outdoors: Apr 1 to May 13Plant for fall: Aug 19 to Sep 9
Start indoors: Apr 8 to Apr 15Transplant outside: May 20 to May 27Sow outdoors: May 13 to May 27Plant for fall: Jul 15 to Jul 29
Start indoors: Apr 8 to Apr 15Sow outdoors: May 13 to May 27Plant for fall: Jul 22 to Aug 5
Start indoors: Apr 8 to Apr 15Sow outdoors: May 13 to May 27
Start indoors: Apr 8 to Apr 15Transplant outside: May 20 to Jun 3
Sow outdoors: Apr 15 to May 13Plant for fall: Jul 8 to Jul 22
Sow outdoors: Apr 15 to May 13Plant for fall: Jul 22 to Aug 5
Sow outdoors: Apr 15 to May 6
Sow outdoors: Apr 22 to May 20Plant for fall: Jul 22 to Aug 5
Sow outdoors: Apr 22 to May 13Plant for fall: Aug 5 to Aug 26
Sow outdoors: May 13 to Jun 3Plant for fall: Jul 15 to Jul 29
Sow outdoors: May 13 to May 27
Transplant outside: May 20 to Jun 10
Plant for fall: Sep 16 to Oct 21
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Glasgow, MT
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 11 – Feb 25 | Apr 8 – Apr 22 | — | — |
| Peppers | Feb 25 – Mar 11 | May 20 – Jun 3 | — | — |
| Eggplant | Feb 25 – Mar 11 | May 20 – Jun 3 | — | — |
| Tomatoes | Mar 11 – Mar 25 | May 13 – May 27 | — | — |
| Lettuce | Mar 11 – Mar 25 | Apr 15 – Apr 29 | Apr 8 – May 13 | Aug 5 – Sep 2 |
| Kale | Mar 11 – Mar 25 | Apr 8 – Apr 22 | Apr 8 – Apr 22 | Jul 22 – Aug 12 |
| Broccoli | Mar 11 – Mar 25 | Apr 22 – May 6 | — | Jun 24 – Jul 15 |
| Cabbage | Mar 11 – Mar 25 | Apr 15 – Apr 29 | — | Jun 24 – Jul 15 |
| Cauliflower | Mar 11 – Mar 25 | Apr 22 – May 6 | — | Jun 24 – Jul 15 |
| Okra | Mar 25 – Apr 8 | May 27 – Jun 10 | May 27 – Jun 10 | — |
| Basil | Mar 25 – Apr 8 | May 13 – May 27 | — | — |
| Peas | — | — | Mar 25 – Apr 15 | Jul 8 – Jul 29 |
| Spinach | — | — | Mar 25 – Apr 15 | Aug 5 – Aug 26 |
| Radishes | — | — | Apr 1 – May 13 | Aug 19 – Sep 9 |
| Cucumbers | Apr 8 – Apr 15 | May 20 – May 27 | May 13 – May 27 | Jul 15 – Jul 29 |
| Zucchini & Summer Squash | Apr 8 – Apr 15 | — | May 13 – May 27 | Jul 22 – Aug 5 |
| Winter Squash & Pumpkins | Apr 8 – Apr 15 | — | May 13 – May 27 | — |
| Melons & Watermelon | Apr 8 – Apr 15 | May 20 – Jun 3 | — | — |
| Carrots | — | — | Apr 15 – May 13 | Jul 8 – Jul 22 |
| Beets | — | — | Apr 15 – May 13 | Jul 22 – Aug 5 |
| Potatoes | — | — | Apr 15 – May 6 | — |
| Swiss Chard | — | — | Apr 22 – May 20 | Jul 22 – Aug 5 |
| Cilantro | — | — | Apr 22 – May 13 | Aug 5 – Aug 26 |
| Green Beans | — | — | May 13 – Jun 3 | Jul 15 – Jul 29 |
| Sweet Corn | — | — | May 13 – May 27 | — |
| Sweet Potatoes | — | May 20 – Jun 10 | — | — |
| Garlic | — | — | — | Sep 16 – Oct 21 |
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 Glasgow Intl Ap, MT weather station, 2 km away (elevation 2,287 ft (697 m)).
Frost dates near Glasgow
- Nashua May 12 · Sep 24
- Saint Marie May 13 · Sep 27
- Fort Peck May 8 · Oct 1
- Vandalia May 15 · Sep 26
- Hinsdale May 15 · Sep 26
- Frazer May 12 · Sep 24
- Larslan Jun 5 · Sep 2
- Richland Jun 5 · Sep 2
- Wolf Point May 8 · Sep 28
- Opheim Jun 1 · Sep 7
Frequently asked questions
When is the last frost in Glasgow, MT?
The median last spring frost in Glasgow, MT is May 6. There is still about a 10% chance of frost after May 18, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Glasgow, MT?
The median first fall frost is September 30, with about a 10% chance of frost before September 17.
How long is the growing season in Glasgow, MT?
About 147 days between the median last spring frost and first fall frost.
What planting zone is Glasgow, MT?
Glasgow, MT is in USDA hardiness zone 4a.