Frost dates for 83321Castleford, ID
The average last spring frost in Castleford is May 17 and the average first fall frost is September 29, giving a typical growing season of about 132 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 17
- Average first fall frost
- Sep 29
- Growing season
- 132 days
Safer after Jun 5 (1-in-10 risk)
Possible by Sep 11 (1-in-10 risk)
Last frost typically in 202 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | May 18 · Jun 5 · Jun 20 | Sep 1 · Sep 16 · Oct 1 | 103 days | 100% |
| Frost / freeze (32°F) | Apr 30 · May 17 · Jun 5 | Sep 11 · Sep 29 · Oct 15 | 132 days | 100% |
| Hard freeze (28°F) | Apr 14 · Apr 30 · May 18 | Sep 26 · Oct 13 · Oct 28 | 162 days | 100% |
Planting calendar for Castleford
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Apr 16 – Jun 22 |
| Tomatoes | Transplant outdoors | Jun 2 – Jun 9 |
| Peppers | Start seeds indoors | Apr 16 – May 17 |
| Peppers | Transplant outdoors | Jun 16 – Jul 17 |
| Eggplant | Start seeds indoors | May 3 – Jun 1 |
| Eggplant | Transplant outdoors | Jun 16 – Jul 17 |
| Cucumbers | Sow outdoors | Jun 16 – Jun 19 |
| Summer squash | Sow outdoors | Jun 2 – Jul 17 |
| Winter squash & pumpkins | Sow outdoors | Jun 16 – Jul 17 |
| Snap beans | Sow outdoors | Jun 2 – Jul 12 |
| Sweet corn | Sow outdoors | Jun 2 – Jun 9 |
| Watermelon & cantaloupe | Sow outdoors | Jun 16 – Jul 17 |
| Okra | Sow outdoors | Jun 9 – Jul 2 |
| Peas | Sow outdoors (spring) | Apr 16 – Jun 1 |
| Potatoes | Plant outdoors (spring) | Apr 16 – Jun 16 |
| Onions | Start seeds indoors (spring) | Mar 5 – Apr 1 |
| Onions | Transplant outdoors (spring) | May 3 – Jun 1 |
| Broccoli | Start seeds indoors (spring) | Mar 29 – May 2 |
| Broccoli | Transplant outdoors (spring) | May 3 – Jun 1 |
| Broccoli | Start seeds indoors (fall) | May 30 – Jun 9 |
| Broccoli | Transplant outdoors (fall) | Jun 29 – Jul 10 |
| Cabbage | Start seeds indoors (spring) | Mar 19 – Apr 16 |
| Cabbage | Transplant outdoors (spring) | Apr 16 – May 17 |
| Cabbage | Start seeds indoors (fall) | May 20 – Jun 19 |
| Cabbage | Transplant outdoors (fall) | Jun 19 – Jul 20 |
| Leaf lettuce | Sow outdoors (spring) | Apr 16 – Jul 2 |
| Leaf lettuce | Sow outdoors (fall) | Jun 19 – Aug 5 |
| Spinach | Sow outdoors (spring) | Apr 9 – May 23 |
| Spinach | Sow outdoors (fall) | Jul 6 – Aug 10 |
| Radishes | Sow outdoors (spring) | Apr 16 – Jun 6 |
| Radishes | Sow outdoors (fall) | Jun 19 – Aug 20 |
| Kale | Sow outdoors (spring) | May 3 – May 23 |
| Kale | Sow outdoors (fall) | Jun 12 – Jul 20 |
| Carrots | Sow outdoors (spring) | May 17 – Jul 2 |
| Carrots | Sow outdoors (fall) | May 20 – Jul 5 |
| Garlic | Plant outdoors (fall) | Sep 19 – Oct 20 |
Where these dates come from
ZIP code 83321 is matched to the NOAA station Castleford 2 N, ID, 3.3 km away, at 3,825 ft elevation (46 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Castleford 2 N, ID (used) | 3,825 ft | May 17 | Sep 29 |
| Buhl #2, ID | 3,800 ft | Apr 25 | Oct 15 |
| Twin Falls Sun Vly Rgnl Ap, ID | 4,151 ft | May 9 | Oct 4 |
| Hagerman 2 Sw, ID | 2,897 ft | May 3 | Oct 1 |
Frost dates near Castleford
- Buhl, ID 83316 · last Apr 25, first Oct 15
- Filer, ID 83328 · last Apr 25, first Oct 15
- Wendell, ID 83355 · last May 2, first Oct 14
- Hagerman, ID 83332 · last May 3, first Oct 1
- Twin Falls, ID 83301 · last Apr 30, first Oct 9
- Jerome, ID 83338 · last May 2, first Oct 14
- Rogerson, ID 83302 · last —, first —
- Kimberly, ID 83341 · last May 6, first Oct 3
Frequently asked questions
- When is the last frost in Castleford, ID?
- For ZIP code 83321, the average last spring frost (32°F) is May 17, based on NOAA 1991-2020 climate normals for the Castleford 2 N, ID weather station. There is a 1-in-10 chance of a frost after June 5.
- When is the first frost in Castleford, ID?
- The average first fall frost (32°F) is September 29. There is a 1-in-10 chance of frost by September 11, so tender plants are at risk from that point on.
- How long is the growing season in 83321?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 132 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.