Mosby, MT frost dates
Last spring frostMay 5median date
First fall frostOct 4median date
Growing season152 daysfrost-free
Hardiness zone4bZone 4b
How Mosby compares
- In 8 years out of 10, the last spring frost in Mosby falls between April 20 and May 26, a 36-day window. The first fall frost falls between September 22 and October 19.
- The median last frost is 14 days earlier than the Montana median of May 19.
- Its 152-day growing season is longer than 96% of the 325 Montana places with a regular frost season (state median 125 days).
- The last frost is typical for zone 4b, where the median is May 8.
- The weather station records an average of 159 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 20 |
| 50% (median) | May 5 |
| 10% (safe for tender plants) | May 26 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 22 |
| 50% (median) | October 4 |
| 90% (late) | October 19 |
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 Mosby, MT
Mosby, MT frost dates — last frost May 5, first frost Oct 4, zone 4b. whenisthelastfrost.com
Crop
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Start indoors: Feb 10 to Feb 24Transplant outside: Apr 7 to Apr 21
Start indoors: Feb 24 to Mar 10Transplant outside: May 19 to Jun 2
Start indoors: Feb 24 to Mar 10Transplant outside: May 19 to Jun 2
Start indoors: Mar 10 to Mar 24Transplant outside: May 12 to May 26
Start indoors: Mar 10 to Mar 24Transplant outside: Apr 14 to Apr 28Sow outdoors: Apr 7 to May 12Plant for fall: Aug 9 to Sep 6
Start indoors: Mar 10 to Mar 24Transplant outside: Apr 7 to Apr 21Sow outdoors: Apr 7 to Apr 21Plant for fall: Jul 26 to Aug 16
Start indoors: Mar 10 to Mar 24Transplant outside: Apr 21 to May 5Plant for fall: Jun 28 to Jul 19
Start indoors: Mar 10 to Mar 24Transplant outside: Apr 14 to Apr 28Plant for fall: Jun 28 to Jul 19
Start indoors: Mar 10 to Mar 24Transplant outside: Apr 21 to May 5Plant for fall: Jun 28 to Jul 19
Start indoors: Mar 24 to Apr 7Transplant outside: May 26 to Jun 9Sow outdoors: May 26 to Jun 9
Start indoors: Mar 24 to Apr 7Transplant outside: May 12 to May 26
Sow outdoors: Mar 24 to Apr 14Plant for fall: Jul 12 to Aug 2
Sow outdoors: Mar 24 to Apr 14Plant for fall: Aug 9 to Aug 30
Sow outdoors: Mar 31 to May 12Plant for fall: Aug 23 to Sep 13
Start indoors: Apr 7 to Apr 14Transplant outside: May 19 to May 26Sow outdoors: May 12 to May 26Plant for fall: Jul 19 to Aug 2
Start indoors: Apr 7 to Apr 14Sow outdoors: May 12 to May 26Plant for fall: Jul 26 to Aug 9
Start indoors: Apr 7 to Apr 14Sow outdoors: May 12 to May 26
Start indoors: Apr 7 to Apr 14Transplant outside: May 19 to Jun 2
Sow outdoors: Apr 14 to May 12Plant for fall: Jul 12 to Jul 26
Sow outdoors: Apr 14 to May 12Plant for fall: Jul 26 to Aug 9
Sow outdoors: Apr 14 to May 5
Sow outdoors: Apr 21 to May 19Plant for fall: Jul 26 to Aug 9
Sow outdoors: Apr 21 to May 12Plant for fall: Aug 9 to Aug 30
Sow outdoors: May 12 to Jun 2Plant for fall: Jul 19 to Aug 2
Sow outdoors: May 12 to May 26
Transplant outside: May 19 to Jun 9
Plant for fall: Sep 20 to Oct 25
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Mosby, MT
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 10 – Feb 24 | Apr 7 – Apr 21 | — | — |
| Peppers | Feb 24 – Mar 10 | May 19 – Jun 2 | — | — |
| Eggplant | Feb 24 – Mar 10 | May 19 – Jun 2 | — | — |
| Tomatoes | Mar 10 – Mar 24 | May 12 – May 26 | — | — |
| Lettuce | Mar 10 – Mar 24 | Apr 14 – Apr 28 | Apr 7 – May 12 | Aug 9 – Sep 6 |
| Kale | Mar 10 – Mar 24 | Apr 7 – Apr 21 | Apr 7 – Apr 21 | Jul 26 – Aug 16 |
| Broccoli | Mar 10 – Mar 24 | Apr 21 – May 5 | — | Jun 28 – Jul 19 |
| Cabbage | Mar 10 – Mar 24 | Apr 14 – Apr 28 | — | Jun 28 – Jul 19 |
| Cauliflower | Mar 10 – Mar 24 | Apr 21 – May 5 | — | Jun 28 – Jul 19 |
| Okra | Mar 24 – Apr 7 | May 26 – Jun 9 | May 26 – Jun 9 | — |
| Basil | Mar 24 – Apr 7 | May 12 – May 26 | — | — |
| Peas | — | — | Mar 24 – Apr 14 | Jul 12 – Aug 2 |
| Spinach | — | — | Mar 24 – Apr 14 | Aug 9 – Aug 30 |
| Radishes | — | — | Mar 31 – May 12 | Aug 23 – Sep 13 |
| Cucumbers | Apr 7 – Apr 14 | May 19 – May 26 | May 12 – May 26 | Jul 19 – Aug 2 |
| Zucchini & Summer Squash | Apr 7 – Apr 14 | — | May 12 – May 26 | Jul 26 – Aug 9 |
| Winter Squash & Pumpkins | Apr 7 – Apr 14 | — | May 12 – May 26 | — |
| Melons & Watermelon | Apr 7 – Apr 14 | May 19 – Jun 2 | — | — |
| Carrots | — | — | Apr 14 – May 12 | Jul 12 – Jul 26 |
| Beets | — | — | Apr 14 – May 12 | Jul 26 – Aug 9 |
| Potatoes | — | — | Apr 14 – May 5 | — |
| Swiss Chard | — | — | Apr 21 – May 19 | Jul 26 – Aug 9 |
| Cilantro | — | — | Apr 21 – May 12 | Aug 9 – Aug 30 |
| Green Beans | — | — | May 12 – Jun 2 | Jul 19 – Aug 2 |
| Sweet Corn | — | — | May 12 – May 26 | — |
| Sweet Potatoes | — | May 19 – Jun 9 | — | — |
| Garlic | — | — | — | Sep 20 – Oct 25 |
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 Mosby 4 Ene, MT weather station, 14 km away (elevation 2,910 ft (887 m)).
Frost dates near Mosby
- Sand Springs May 5 · Oct 4
- Melstone May 10 · Sep 29
- Sumatra May 10 · Sep 29
- Winnett May 16 · Sep 28
- Ingomar May 21 · Sep 19
- Musselshell May 10 · Sep 29
- Teigen May 20 · Sep 24
- Brusett May 18 · Sep 20
- Roundup May 20 · Sep 21
- Hysham May 10 · Sep 29
Frequently asked questions
When is the last frost in Mosby, MT?
The median last spring frost in Mosby, MT is May 5. There is still about a 10% chance of frost after May 26, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Mosby, MT?
The median first fall frost is October 4, with about a 10% chance of frost before September 22.
How long is the growing season in Mosby, MT?
About 152 days between the median last spring frost and first fall frost.
What planting zone is Mosby, MT?
Mosby, MT is in USDA hardiness zone 4b.