Castleford, ID frost dates
Last spring frostMay 17median date
First fall frostSep 29median date
Growing season135 daysfrost-free
Hardiness zone6bZone 6b
How Castleford compares
- In 8 years out of 10, the last spring frost in Castleford falls between April 30 and June 5, a 36-day window. The first fall frost falls between September 11 and October 15.
- The median last frost is 3 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 25 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 146 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 30 |
| 50% (median) | May 17 |
| 10% (safe for tender plants) | June 5 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 11 |
| 50% (median) | September 29 |
| 90% (late) | October 15 |
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 Castleford, ID
Castleford, ID frost dates — last frost May 17, first frost Sep 29, zone 6b. whenisthelastfrost.com
Crop
JFMAMJJASOND
Start indoors: Feb 22 to Mar 8Transplant outside: Apr 19 to May 3
Start indoors: Mar 8 to Mar 22Transplant outside: May 31 to Jun 14
Start indoors: Mar 8 to Mar 22Transplant outside: May 31 to Jun 14
Start indoors: Mar 22 to Apr 5Transplant outside: May 24 to Jun 7
Start indoors: Mar 22 to Apr 5Transplant outside: Apr 26 to May 10Sow outdoors: Apr 19 to May 24Plant for fall: Aug 4 to Sep 1
Start indoors: Mar 22 to Apr 5Transplant outside: Apr 19 to May 3Sow outdoors: Apr 19 to May 3Plant for fall: Jul 21 to Aug 11
Start indoors: Mar 22 to Apr 5Transplant outside: May 3 to May 17Plant for fall: Jun 23 to Jul 14
Start indoors: Mar 22 to Apr 5Transplant outside: Apr 26 to May 10Plant for fall: Jun 23 to Jul 14
Start indoors: Mar 22 to Apr 5Transplant outside: May 3 to May 17Plant for fall: Jun 23 to Jul 14
Start indoors: Apr 5 to Apr 19Transplant outside: Jun 7 to Jun 21Sow outdoors: Jun 7 to Jun 21
Start indoors: Apr 5 to Apr 19Transplant outside: May 24 to Jun 7
Sow outdoors: Apr 5 to Apr 26Plant for fall: Jul 7 to Jul 28
Sow outdoors: Apr 5 to Apr 26Plant for fall: Aug 4 to Aug 25
Sow outdoors: Apr 12 to May 24Plant for fall: Aug 18 to Sep 8
Start indoors: Apr 19 to Apr 26Transplant outside: May 31 to Jun 7Sow outdoors: May 24 to Jun 7Plant for fall: Jul 14 to Jul 28
Start indoors: Apr 19 to Apr 26Sow outdoors: May 24 to Jun 7Plant for fall: Jul 21 to Aug 4
Start indoors: Apr 19 to Apr 26Sow outdoors: May 24 to Jun 7
Start indoors: Apr 19 to Apr 26Transplant outside: May 31 to Jun 14
Sow outdoors: Apr 26 to May 24Plant for fall: Jul 7 to Jul 21
Sow outdoors: Apr 26 to May 24Plant for fall: Jul 21 to Aug 4
Sow outdoors: Apr 26 to May 17
Sow outdoors: May 3 to May 31Plant for fall: Jul 21 to Aug 4
Sow outdoors: May 3 to May 24Plant for fall: Aug 4 to Aug 25
Sow outdoors: May 24 to Jun 14Plant for fall: Jul 14 to Jul 28
Sow outdoors: May 24 to Jun 7
Transplant outside: May 31 to Jun 21
Plant for fall: Sep 15 to Oct 20
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Castleford, ID
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 22 – Mar 8 | Apr 19 – May 3 | — | — |
| Peppers | Mar 8 – Mar 22 | May 31 – Jun 14 | — | — |
| Eggplant | Mar 8 – Mar 22 | May 31 – Jun 14 | — | — |
| Tomatoes | Mar 22 – Apr 5 | May 24 – Jun 7 | — | — |
| Lettuce | Mar 22 – Apr 5 | Apr 26 – May 10 | Apr 19 – May 24 | Aug 4 – Sep 1 |
| Kale | Mar 22 – Apr 5 | Apr 19 – May 3 | Apr 19 – May 3 | Jul 21 – Aug 11 |
| Broccoli | Mar 22 – Apr 5 | May 3 – May 17 | — | Jun 23 – Jul 14 |
| Cabbage | Mar 22 – Apr 5 | Apr 26 – May 10 | — | Jun 23 – Jul 14 |
| Cauliflower | Mar 22 – Apr 5 | May 3 – May 17 | — | Jun 23 – Jul 14 |
| Okra | Apr 5 – Apr 19 | Jun 7 – Jun 21 | Jun 7 – Jun 21 | — |
| Basil | Apr 5 – Apr 19 | May 24 – Jun 7 | — | — |
| Peas | — | — | Apr 5 – Apr 26 | Jul 7 – Jul 28 |
| Spinach | — | — | Apr 5 – Apr 26 | Aug 4 – Aug 25 |
| Radishes | — | — | Apr 12 – May 24 | Aug 18 – Sep 8 |
| Cucumbers | Apr 19 – Apr 26 | May 31 – Jun 7 | May 24 – Jun 7 | Jul 14 – Jul 28 |
| Zucchini & Summer Squash | Apr 19 – Apr 26 | — | May 24 – Jun 7 | Jul 21 – Aug 4 |
| Winter Squash & Pumpkins | Apr 19 – Apr 26 | — | May 24 – Jun 7 | — |
| Melons & Watermelon | Apr 19 – Apr 26 | May 31 – Jun 14 | — | — |
| Carrots | — | — | Apr 26 – May 24 | Jul 7 – Jul 21 |
| Beets | — | — | Apr 26 – May 24 | Jul 21 – Aug 4 |
| Potatoes | — | — | Apr 26 – May 17 | — |
| Swiss Chard | — | — | May 3 – May 31 | Jul 21 – Aug 4 |
| Cilantro | — | — | May 3 – May 24 | Aug 4 – Aug 25 |
| Green Beans | — | — | May 24 – Jun 14 | Jul 14 – Jul 28 |
| Sweet Corn | — | — | May 24 – Jun 7 | — |
| Sweet Potatoes | — | May 31 – Jun 21 | — | — |
| Garlic | — | — | — | Sep 15 – Oct 20 |
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 Castleford 2 N, ID weather station, 3 km away (elevation 3,825 ft (1,166 m)).
Frost dates near Castleford
- Buhl Apr 25 · Oct 15
- Filer Apr 25 · Oct 15
- Wendell May 2 · Oct 14
- Hagerman May 3 · Oct 1
- Twin Falls Apr 30 · Oct 9
- Jerome May 2 · Oct 14
- Rogerson frost any month
- Kimberly May 6 · Oct 3
- Hansen May 6 · Oct 3
- Bliss May 3 · Oct 1
Frequently asked questions
When is the last frost in Castleford, ID?
The median last spring frost in Castleford, ID is May 17. There is still about a 10% chance of frost after June 5, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Castleford, ID?
The median first fall frost is September 29, with about a 10% chance of frost before September 11.
How long is the growing season in Castleford, ID?
About 135 days between the median last spring frost and first fall frost.
What planting zone is Castleford, ID?
Castleford, ID is in USDA hardiness zone 6b.