Frost dates for 51301Spencer, IA
The average last spring frost in Spencer is May 1 and the average first fall frost is October 3, giving a typical growing season of about 154 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 1
- Average first fall frost
- Oct 3
- Growing season
- 154 days
Safer after May 14 (1-in-10 risk)
Possible by Sep 20 (1-in-10 risk)
Last frost typically in 186 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) | Apr 29 · May 10 · May 23 | Sep 11 · Sep 24 · Oct 7 | 137 days | 100% |
| Frost / freeze (32°F) | Apr 18 · May 1 · May 14 | Sep 20 · Oct 3 · Oct 17 | 154 days | 100% |
| Hard freeze (28°F) | Apr 8 · Apr 22 · May 5 | Sep 28 · Oct 14 · Oct 27 | 174 days | 100% |
Planting calendar for Spencer
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 | Mar 31 – Jun 6 |
| Tomatoes | Transplant outdoors | May 17 – Jun 13 |
| Peppers | Start seeds indoors | Mar 31 – May 1 |
| Peppers | Transplant outdoors | May 31 – Jul 1 |
| Eggplant | Start seeds indoors | Apr 17 – May 16 |
| Eggplant | Transplant outdoors | May 31 – Jul 1 |
| Cucumbers | Sow outdoors | May 31 – Jun 23 |
| Summer squash | Sow outdoors | May 17 – Jul 1 |
| Winter squash & pumpkins | Sow outdoors | May 31 – Jul 1 |
| Snap beans | Sow outdoors | May 17 – Jul 16 |
| Sweet corn | Sow outdoors | May 17 – Jun 13 |
| Watermelon & cantaloupe | Sow outdoors | May 31 – Jul 1 |
| Okra | Sow outdoors | May 24 – Jun 16 |
| Peas | Sow outdoors (spring) | Mar 31 – May 16 |
| Potatoes | Plant outdoors (spring) | Mar 31 – May 31 |
| Onions | Start seeds indoors (spring) | Feb 17 – Mar 16 |
| Onions | Transplant outdoors (spring) | Apr 17 – May 16 |
| Broccoli | Start seeds indoors (spring) | Mar 13 – Apr 16 |
| Broccoli | Transplant outdoors (spring) | Apr 17 – May 16 |
| Broccoli | Start seeds indoors (fall) | Jun 3 – Jun 13 |
| Broccoli | Transplant outdoors (fall) | Jul 3 – Jul 14 |
| Cabbage | Start seeds indoors (spring) | Mar 3 – Mar 31 |
| Cabbage | Transplant outdoors (spring) | Mar 31 – May 1 |
| Cabbage | Start seeds indoors (fall) | May 24 – Jun 23 |
| Cabbage | Transplant outdoors (fall) | Jun 23 – Jul 24 |
| Leaf lettuce | Sow outdoors (spring) | Mar 31 – Jun 16 |
| Leaf lettuce | Sow outdoors (fall) | Jun 23 – Aug 9 |
| Spinach | Sow outdoors (spring) | Mar 24 – May 7 |
| Spinach | Sow outdoors (fall) | Jul 10 – Aug 14 |
| Radishes | Sow outdoors (spring) | Mar 31 – May 21 |
| Radishes | Sow outdoors (fall) | Jun 23 – Aug 24 |
| Kale | Sow outdoors (spring) | Apr 17 – May 7 |
| Kale | Sow outdoors (fall) | Jun 16 – Jul 24 |
| Carrots | Sow outdoors (spring) | May 1 – Jun 16 |
| Carrots | Sow outdoors (fall) | May 24 – Jul 9 |
| Garlic | Plant outdoors (fall) | Sep 23 – Oct 24 |
Where these dates come from
ZIP code 51301 is matched to the NOAA station Spencer 1 N, IA, 2.2 km away, at 1,326 ft elevation (10 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Spencer 1 N, IA (used) | 1,326 ft | May 1 | Oct 3 |
| Spencer Muni Ap, IA | 1,338 ft | May 2 | Oct 2 |
| Milford 4 Nw, IA | 1,402 ft | May 1 | Oct 6 |
| Sioux Rapids 4 E, IA | 1,420 ft | Apr 30 | Oct 5 |
Frost dates near Spencer
- Fostoria, IA 51340 · last May 1, first Oct 3
- Dickens, IA 51333 · last May 1, first Oct 3
- Greenville, IA 51343 · last Apr 30, first Oct 5
- Everly, IA 51338 · last May 2, first Oct 2
- Royal, IA 51357 · last May 2, first Oct 2
- Gillett Grove, IA 51341 · last Apr 30, first Oct 5
- Milford, IA 51351 · last May 1, first Oct 6
- Ruthven, IA 51358 · last May 1, first Oct 3
Frequently asked questions
- When is the last frost in Spencer, IA?
- For ZIP code 51301, the average last spring frost (32°F) is May 1, based on NOAA 1991-2020 climate normals for the Spencer 1 N, IA weather station. There is a 1-in-10 chance of a frost after May 14.
- When is the first frost in Spencer, IA?
- The average first fall frost (32°F) is October 3. There is a 1-in-10 chance of frost by September 20, so tender plants are at risk from that point on.
- How long is the growing season in 51301?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 154 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.