Princeton, ID frost dates
Last spring frostMay 15median date
First fall frostSep 21median date
Growing season129 daysfrost-free
Hardiness zone6bZone 6b
How Princeton compares
- In 8 years out of 10, the last spring frost in Princeton falls between April 30 and June 2, a 33-day window. The first fall frost falls between August 31 and October 7.
- The median last frost is 1 day later than the Idaho median of May 14.
- Its 129-day growing season is longer than 34% of the 244 Idaho places with a regular frost season (state median 138 days).
- The last frost is 23 days later than the zone 6b median of Apr 22. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 6b chart.
- The weather station records an average of 153 nights a year at or below 32°F.
- Compared with Spokane, WA, 95 km away, the last frost here is 19 days later than there and the growing season is 43 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 30 |
| 50% (median) | May 15 |
| 10% (safe for tender plants) | June 2 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | August 31 |
| 50% (median) | September 21 |
| 90% (late) | October 7 |
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 Princeton, ID
Princeton, ID frost dates — last frost May 15, first frost Sep 21, zone 6b. whenisthelastfrost.com
Crop
JFMAMJJASOND
Start indoors: Feb 20 to Mar 6Transplant outside: Apr 17 to May 1
Start indoors: Mar 6 to Mar 20Transplant outside: May 29 to Jun 12
Start indoors: Mar 6 to Mar 20Transplant outside: May 29 to Jun 12
Start indoors: Mar 20 to Apr 3Transplant outside: May 22 to Jun 5
Start indoors: Mar 20 to Apr 3Transplant outside: Apr 24 to May 8Sow outdoors: Apr 17 to May 22Plant for fall: Jul 27 to Aug 24
Start indoors: Mar 20 to Apr 3Transplant outside: Apr 17 to May 1Sow outdoors: Apr 17 to May 1Plant for fall: Jul 13 to Aug 3
Start indoors: Mar 20 to Apr 3Transplant outside: May 1 to May 15Plant for fall: Jun 15 to Jul 6
Start indoors: Mar 20 to Apr 3Transplant outside: Apr 24 to May 8Plant for fall: Jun 15 to Jul 6
Start indoors: Mar 20 to Apr 3Transplant outside: May 1 to May 15Plant for fall: Jun 15 to Jul 6
Start indoors: Apr 3 to Apr 17Transplant outside: Jun 5 to Jun 19Sow outdoors: Jun 5 to Jun 19
Start indoors: Apr 3 to Apr 17Transplant outside: May 22 to Jun 5
Sow outdoors: Apr 3 to Apr 24Plant for fall: Jun 29 to Jul 20
Sow outdoors: Apr 3 to Apr 24Plant for fall: Jul 27 to Aug 17
Sow outdoors: Apr 10 to May 22Plant for fall: Aug 10 to Aug 31
Start indoors: Apr 17 to Apr 24Transplant outside: May 29 to Jun 5Sow outdoors: May 22 to Jun 5Plant for fall: Jul 6 to Jul 20
Start indoors: Apr 17 to Apr 24Sow outdoors: May 22 to Jun 5Plant for fall: Jul 13 to Jul 27
Start indoors: Apr 17 to Apr 24Sow outdoors: May 22 to Jun 5
Start indoors: Apr 17 to Apr 24Transplant outside: May 29 to Jun 12
Sow outdoors: Apr 24 to May 22Plant for fall: Jun 29 to Jul 13
Sow outdoors: Apr 24 to May 22Plant for fall: Jul 13 to Jul 27
Sow outdoors: Apr 24 to May 15
Sow outdoors: May 1 to May 29Plant for fall: Jul 13 to Jul 27
Sow outdoors: May 1 to May 22Plant for fall: Jul 27 to Aug 17
Sow outdoors: May 22 to Jun 12Plant for fall: Jul 6 to Jul 20
Sow outdoors: May 22 to Jun 5
Transplant outside: May 29 to Jun 19
Plant for fall: Sep 7 to Oct 12
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Princeton, ID
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 20 – Mar 6 | Apr 17 – May 1 | — | — |
| Peppers | Mar 6 – Mar 20 | May 29 – Jun 12 | — | — |
| Eggplant | Mar 6 – Mar 20 | May 29 – Jun 12 | — | — |
| Tomatoes | Mar 20 – Apr 3 | May 22 – Jun 5 | — | — |
| Lettuce | Mar 20 – Apr 3 | Apr 24 – May 8 | Apr 17 – May 22 | Jul 27 – Aug 24 |
| Kale | Mar 20 – Apr 3 | Apr 17 – May 1 | Apr 17 – May 1 | Jul 13 – Aug 3 |
| Broccoli | Mar 20 – Apr 3 | May 1 – May 15 | — | Jun 15 – Jul 6 |
| Cabbage | Mar 20 – Apr 3 | Apr 24 – May 8 | — | Jun 15 – Jul 6 |
| Cauliflower | Mar 20 – Apr 3 | May 1 – May 15 | — | Jun 15 – Jul 6 |
| Okra | Apr 3 – Apr 17 | Jun 5 – Jun 19 | Jun 5 – Jun 19 | — |
| Basil | Apr 3 – Apr 17 | May 22 – Jun 5 | — | — |
| Peas | — | — | Apr 3 – Apr 24 | Jun 29 – Jul 20 |
| Spinach | — | — | Apr 3 – Apr 24 | Jul 27 – Aug 17 |
| Radishes | — | — | Apr 10 – May 22 | Aug 10 – Aug 31 |
| Cucumbers | Apr 17 – Apr 24 | May 29 – Jun 5 | May 22 – Jun 5 | Jul 6 – Jul 20 |
| Zucchini & Summer Squash | Apr 17 – Apr 24 | — | May 22 – Jun 5 | Jul 13 – Jul 27 |
| Winter Squash & Pumpkins | Apr 17 – Apr 24 | — | May 22 – Jun 5 | — |
| Melons & Watermelon | Apr 17 – Apr 24 | May 29 – Jun 12 | — | — |
| Carrots | — | — | Apr 24 – May 22 | Jun 29 – Jul 13 |
| Beets | — | — | Apr 24 – May 22 | Jul 13 – Jul 27 |
| Potatoes | — | — | Apr 24 – May 15 | — |
| Swiss Chard | — | — | May 1 – May 29 | Jul 13 – Jul 27 |
| Cilantro | — | — | May 1 – May 22 | Jul 27 – Aug 17 |
| Green Beans | — | — | May 22 – Jun 12 | Jul 6 – Jul 20 |
| Sweet Corn | — | — | May 22 – Jun 5 | — |
| Sweet Potatoes | — | May 29 – Jun 19 | — | — |
| Garlic | — | — | — | Sep 7 – Oct 12 |
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 Potlatch 3 Nne, ID weather station, 7 km away (elevation 2,759 ft (841 m)).
Frost dates near Princeton
- Potlatch May 15 · Sep 21
- Harvard May 15 · Sep 21
- Viola May 15 · Sep 21
- Troy frost any month
- Moscow frost any month
- Deary May 16 · Sep 23
- Desmet May 15 · Sep 21
- Tensed May 11 · Oct 5
- Bovill May 16 · Sep 23
- Kendrick Apr 20 · Oct 20
Frequently asked questions
When is the last frost in Princeton, ID?
The median last spring frost in Princeton, ID is May 15. There is still about a 10% chance of frost after June 2, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Princeton, ID?
The median first fall frost is September 21, with about a 10% chance of frost before August 31.
How long is the growing season in Princeton, ID?
About 129 days between the median last spring frost and first fall frost.
What planting zone is Princeton, ID?
Princeton, ID is in USDA hardiness zone 6b.