Spencer, ID frost dates
Last spring frostMay 18median date
First fall frostSep 30median date
Growing season135 daysfrost-free
Hardiness zone5bZone 5b
How Spencer compares
- In 8 years out of 10, the last spring frost in Spencer falls between May 3 and June 9, a 37-day window. The first fall frost falls between September 14 and October 16.
- The median last frost is 4 days later than the Idaho median of May 14.
- Its 135-day growing season is longer than 42% of the 244 Idaho places with a regular frost season (state median 138 days).
- The last frost is 17 days later than the zone 5b median of May 1. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 5b chart.
- The weather station records an average of 178 nights a year at or below 32°F.
- Compared with Idaho Falls, ID, 99 km away, the last frost here is 9 days later than there and the growing season is 10 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 3 |
| 50% (median) | May 18 |
| 10% (safe for tender plants) | June 9 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 14 |
| 50% (median) | September 30 |
| 90% (late) | October 16 |
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 Spencer, ID
Spencer, ID frost dates — last frost May 18, first frost Sep 30, zone 5b. whenisthelastfrost.com
Crop
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Start indoors: Feb 23 to Mar 9Transplant outside: Apr 20 to May 4
Start indoors: Mar 9 to Mar 23Transplant outside: Jun 1 to Jun 15
Start indoors: Mar 9 to Mar 23Transplant outside: Jun 1 to Jun 15
Start indoors: Mar 23 to Apr 6Transplant outside: May 25 to Jun 8
Start indoors: Mar 23 to Apr 6Transplant outside: Apr 27 to May 11Sow outdoors: Apr 20 to May 25Plant for fall: Aug 5 to Sep 2
Start indoors: Mar 23 to Apr 6Transplant outside: Apr 20 to May 4Sow outdoors: Apr 20 to May 4Plant for fall: Jul 22 to Aug 12
Start indoors: Mar 23 to Apr 6Transplant outside: May 4 to May 18Plant for fall: Jun 24 to Jul 15
Start indoors: Mar 23 to Apr 6Transplant outside: Apr 27 to May 11Plant for fall: Jun 24 to Jul 15
Start indoors: Mar 23 to Apr 6Transplant outside: May 4 to May 18Plant for fall: Jun 24 to Jul 15
Start indoors: Apr 6 to Apr 20Transplant outside: Jun 8 to Jun 22Sow outdoors: Jun 8 to Jun 22
Start indoors: Apr 6 to Apr 20Transplant outside: May 25 to Jun 8
Sow outdoors: Apr 6 to Apr 27Plant for fall: Jul 8 to Jul 29
Sow outdoors: Apr 6 to Apr 27Plant for fall: Aug 5 to Aug 26
Sow outdoors: Apr 13 to May 25Plant for fall: Aug 19 to Sep 9
Start indoors: Apr 20 to Apr 27Transplant outside: Jun 1 to Jun 8Sow outdoors: May 25 to Jun 8Plant for fall: Jul 15 to Jul 29
Start indoors: Apr 20 to Apr 27Sow outdoors: May 25 to Jun 8Plant for fall: Jul 22 to Aug 5
Start indoors: Apr 20 to Apr 27Sow outdoors: May 25 to Jun 8
Start indoors: Apr 20 to Apr 27Transplant outside: Jun 1 to Jun 15
Sow outdoors: Apr 27 to May 25Plant for fall: Jul 8 to Jul 22
Sow outdoors: Apr 27 to May 25Plant for fall: Jul 22 to Aug 5
Sow outdoors: Apr 27 to May 18
Sow outdoors: May 4 to Jun 1Plant for fall: Jul 22 to Aug 5
Sow outdoors: May 4 to May 25Plant for fall: Aug 5 to Aug 26
Sow outdoors: May 25 to Jun 15Plant for fall: Jul 15 to Jul 29
Sow outdoors: May 25 to Jun 8
Transplant outside: Jun 1 to Jun 22
Plant for fall: Sep 16 to Oct 21
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Spencer, ID
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 23 – Mar 9 | Apr 20 – May 4 | — | — |
| Peppers | Mar 9 – Mar 23 | Jun 1 – Jun 15 | — | — |
| Eggplant | Mar 9 – Mar 23 | Jun 1 – Jun 15 | — | — |
| Tomatoes | Mar 23 – Apr 6 | May 25 – Jun 8 | — | — |
| Lettuce | Mar 23 – Apr 6 | Apr 27 – May 11 | Apr 20 – May 25 | Aug 5 – Sep 2 |
| Kale | Mar 23 – Apr 6 | Apr 20 – May 4 | Apr 20 – May 4 | Jul 22 – Aug 12 |
| Broccoli | Mar 23 – Apr 6 | May 4 – May 18 | — | Jun 24 – Jul 15 |
| Cabbage | Mar 23 – Apr 6 | Apr 27 – May 11 | — | Jun 24 – Jul 15 |
| Cauliflower | Mar 23 – Apr 6 | May 4 – May 18 | — | Jun 24 – Jul 15 |
| Okra | Apr 6 – Apr 20 | Jun 8 – Jun 22 | Jun 8 – Jun 22 | — |
| Basil | Apr 6 – Apr 20 | May 25 – Jun 8 | — | — |
| Peas | — | — | Apr 6 – Apr 27 | Jul 8 – Jul 29 |
| Spinach | — | — | Apr 6 – Apr 27 | Aug 5 – Aug 26 |
| Radishes | — | — | Apr 13 – May 25 | Aug 19 – Sep 9 |
| Cucumbers | Apr 20 – Apr 27 | Jun 1 – Jun 8 | May 25 – Jun 8 | Jul 15 – Jul 29 |
| Zucchini & Summer Squash | Apr 20 – Apr 27 | — | May 25 – Jun 8 | Jul 22 – Aug 5 |
| Winter Squash & Pumpkins | Apr 20 – Apr 27 | — | May 25 – Jun 8 | — |
| Melons & Watermelon | Apr 20 – Apr 27 | Jun 1 – Jun 15 | — | — |
| Carrots | — | — | Apr 27 – May 25 | Jul 8 – Jul 22 |
| Beets | — | — | Apr 27 – May 25 | Jul 22 – Aug 5 |
| Potatoes | — | — | Apr 27 – May 18 | — |
| Swiss Chard | — | — | May 4 – Jun 1 | Jul 22 – Aug 5 |
| Cilantro | — | — | May 4 – May 25 | Aug 5 – Aug 26 |
| Green Beans | — | — | May 25 – Jun 15 | Jul 15 – Jul 29 |
| Sweet Corn | — | — | May 25 – Jun 8 | — |
| Sweet Potatoes | — | Jun 1 – Jun 22 | — | — |
| 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 Dubois Exp Stn, ID weather station, 13 km away (elevation 5,449 ft (1,661 m)).
Frost dates near Spencer
- Dubois May 18 · Sep 30
- Macks Inn frost any month
- Hamer Jun 3 · Sep 11
- Monteview Jun 12 · Sep 7
- Parker May 17 · Sep 22
- Saint Anthony May 17 · Sep 22
- Terreton Jun 3 · Sep 11
- Chester May 21 · Sep 21
- Island Park frost any month
- Teton May 29 · Sep 13
Frequently asked questions
When is the last frost in Spencer, ID?
The median last spring frost in Spencer, ID is May 18. There is still about a 10% chance of frost after June 9, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Spencer, ID?
The median first fall frost is September 30, with about a 10% chance of frost before September 14.
How long is the growing season in Spencer, ID?
About 135 days between the median last spring frost and first fall frost.
What planting zone is Spencer, ID?
Spencer, ID is in USDA hardiness zone 5b.