Otter, MT frost dates
Last spring frostMay 14median date
First fall frostSep 30median date
Growing season139 daysfrost-free
Hardiness zone5aZone 5a
How Otter compares
- In 8 years out of 10, the last spring frost in Otter falls between April 30 and May 29, a 29-day window. The first fall frost falls between September 17 and October 13.
- The median last frost is 5 days earlier than the Montana median of May 19.
- Its 139-day growing season is longer than 79% of the 325 Montana places with a regular frost season (state median 125 days).
- The last frost is 11 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 168 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 30 |
| 50% (median) | May 14 |
| 10% (safe for tender plants) | May 29 |
| 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 Otter, MT
Otter, MT frost dates — last frost May 14, first frost Sep 30, zone 5a. whenisthelastfrost.com
Crop
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Start indoors: Feb 19 to Mar 5Transplant outside: Apr 16 to Apr 30
Start indoors: Mar 5 to Mar 19Transplant outside: May 28 to Jun 11
Start indoors: Mar 5 to Mar 19Transplant outside: May 28 to Jun 11
Start indoors: Mar 19 to Apr 2Transplant outside: May 21 to Jun 4
Start indoors: Mar 19 to Apr 2Transplant outside: Apr 23 to May 7Sow outdoors: Apr 16 to May 21Plant for fall: Aug 5 to Sep 2
Start indoors: Mar 19 to Apr 2Transplant outside: Apr 16 to Apr 30Sow outdoors: Apr 16 to Apr 30Plant for fall: Jul 22 to Aug 12
Start indoors: Mar 19 to Apr 2Transplant outside: Apr 30 to May 14Plant for fall: Jun 24 to Jul 15
Start indoors: Mar 19 to Apr 2Transplant outside: Apr 23 to May 7Plant for fall: Jun 24 to Jul 15
Start indoors: Mar 19 to Apr 2Transplant outside: Apr 30 to May 14Plant for fall: Jun 24 to Jul 15
Start indoors: Apr 2 to Apr 16Transplant outside: Jun 4 to Jun 18Sow outdoors: Jun 4 to Jun 18
Start indoors: Apr 2 to Apr 16Transplant outside: May 21 to Jun 4
Sow outdoors: Apr 2 to Apr 23Plant for fall: Jul 8 to Jul 29
Sow outdoors: Apr 2 to Apr 23Plant for fall: Aug 5 to Aug 26
Sow outdoors: Apr 9 to May 21Plant for fall: Aug 19 to Sep 9
Start indoors: Apr 16 to Apr 23Transplant outside: May 28 to Jun 4Sow outdoors: May 21 to Jun 4Plant for fall: Jul 15 to Jul 29
Start indoors: Apr 16 to Apr 23Sow outdoors: May 21 to Jun 4Plant for fall: Jul 22 to Aug 5
Start indoors: Apr 16 to Apr 23Sow outdoors: May 21 to Jun 4
Start indoors: Apr 16 to Apr 23Transplant outside: May 28 to Jun 11
Sow outdoors: Apr 23 to May 21Plant for fall: Jul 8 to Jul 22
Sow outdoors: Apr 23 to May 21Plant for fall: Jul 22 to Aug 5
Sow outdoors: Apr 23 to May 14
Sow outdoors: Apr 30 to May 28Plant for fall: Jul 22 to Aug 5
Sow outdoors: Apr 30 to May 21Plant for fall: Aug 5 to Aug 26
Sow outdoors: May 21 to Jun 11Plant for fall: Jul 15 to Jul 29
Sow outdoors: May 21 to Jun 4
Transplant outside: May 28 to Jun 18
Plant for fall: Sep 16 to Oct 21
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Otter, MT
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 19 – Mar 5 | Apr 16 – Apr 30 | — | — |
| Peppers | Mar 5 – Mar 19 | May 28 – Jun 11 | — | — |
| Eggplant | Mar 5 – Mar 19 | May 28 – Jun 11 | — | — |
| Tomatoes | Mar 19 – Apr 2 | May 21 – Jun 4 | — | — |
| Lettuce | Mar 19 – Apr 2 | Apr 23 – May 7 | Apr 16 – May 21 | Aug 5 – Sep 2 |
| Kale | Mar 19 – Apr 2 | Apr 16 – Apr 30 | Apr 16 – Apr 30 | Jul 22 – Aug 12 |
| Broccoli | Mar 19 – Apr 2 | Apr 30 – May 14 | — | Jun 24 – Jul 15 |
| Cabbage | Mar 19 – Apr 2 | Apr 23 – May 7 | — | Jun 24 – Jul 15 |
| Cauliflower | Mar 19 – Apr 2 | Apr 30 – May 14 | — | Jun 24 – Jul 15 |
| Okra | Apr 2 – Apr 16 | Jun 4 – Jun 18 | Jun 4 – Jun 18 | — |
| Basil | Apr 2 – Apr 16 | May 21 – Jun 4 | — | — |
| Peas | — | — | Apr 2 – Apr 23 | Jul 8 – Jul 29 |
| Spinach | — | — | Apr 2 – Apr 23 | Aug 5 – Aug 26 |
| Radishes | — | — | Apr 9 – May 21 | Aug 19 – Sep 9 |
| Cucumbers | Apr 16 – Apr 23 | May 28 – Jun 4 | May 21 – Jun 4 | Jul 15 – Jul 29 |
| Zucchini & Summer Squash | Apr 16 – Apr 23 | — | May 21 – Jun 4 | Jul 22 – Aug 5 |
| Winter Squash & Pumpkins | Apr 16 – Apr 23 | — | May 21 – Jun 4 | — |
| Melons & Watermelon | Apr 16 – Apr 23 | May 28 – Jun 11 | — | — |
| Carrots | — | — | Apr 23 – May 21 | Jul 8 – Jul 22 |
| Beets | — | — | Apr 23 – May 21 | Jul 22 – Aug 5 |
| Potatoes | — | — | Apr 23 – May 14 | — |
| Swiss Chard | — | — | Apr 30 – May 28 | Jul 22 – Aug 5 |
| Cilantro | — | — | Apr 30 – May 21 | Aug 5 – Aug 26 |
| Green Beans | — | — | May 21 – Jun 11 | Jul 15 – Jul 29 |
| Sweet Corn | — | — | May 21 – Jun 4 | — |
| Sweet Potatoes | — | May 28 – Jun 18 | — | — |
| 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 Leiter 9n, WY weather station, 29 km away (elevation 4,160 ft (1,268 m)).
Frost dates near Otter
- Birney May 23 · Sep 15
- Ashland May 18 · Sep 22
- Decker May 18 · Sep 24
- Biddle May 14 · Sep 28
- Lame Deer May 23 · Sep 15
- Olive May 16 · Sep 28
- Broadus May 16 · Sep 28
- Busby May 23 · Sep 15
- Boyes May 16 · Sep 28
- Volborg May 18 · Sep 22
Frequently asked questions
When is the last frost in Otter, MT?
The median last spring frost in Otter, MT is May 14. There is still about a 10% chance of frost after May 29, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Otter, 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 Otter, MT?
About 139 days between the median last spring frost and first fall frost.
What planting zone is Otter, MT?
Otter, MT is in USDA hardiness zone 5a.