Frost dates for 52638Middletown, IA
The average last spring frost in Middletown is April 15 and the average first fall frost is October 20, giving a typical growing season of about 187 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 15
- Average first fall frost
- Oct 20
- Growing season
- 187 days
Safer after May 1 (1-in-10 risk)
Possible by Oct 6 (1-in-10 risk)
Last frost typically in 167 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 13 · Apr 28 · May 12 | Sep 25 · Oct 11 · Oct 22 | 166 days | 100% |
| Frost / freeze (32°F) | Apr 2 · Apr 15 · May 1 | Oct 6 · Oct 20 · Nov 1 | 187 days | 100% |
| Hard freeze (28°F) | Mar 20 · Apr 5 · Apr 22 | Oct 18 · Oct 31 · Nov 13 | 207 days | 100% |
Planting calendar for Middletown
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 15 – May 21 |
| Tomatoes | Transplant outdoors | May 1 – Jun 30 |
| Peppers | Start seeds indoors | Mar 15 – Apr 15 |
| Peppers | Transplant outdoors | May 15 – Jun 15 |
| Eggplant | Start seeds indoors | Apr 1 – Apr 30 |
| Eggplant | Transplant outdoors | May 15 – Jun 15 |
| Cucumbers | Sow outdoors | May 15 – Jul 10 |
| Summer squash | Sow outdoors | May 1 – Jun 15 |
| Winter squash & pumpkins | Sow outdoors | May 15 – Jun 15 |
| Snap beans | Sow outdoors | May 1 – Aug 2 |
| Sweet corn | Sow outdoors | May 1 – Jun 30 |
| Watermelon & cantaloupe | Sow outdoors | May 15 – Jun 15 |
| Okra | Sow outdoors | May 8 – May 31 |
| Peas | Sow outdoors (spring) | Mar 15 – Apr 30 |
| Potatoes | Plant outdoors (spring) | Mar 15 – May 15 |
| Onions | Start seeds indoors (spring) | Feb 1 – Feb 28 |
| Onions | Transplant outdoors (spring) | Apr 1 – Apr 30 |
| Broccoli | Start seeds indoors (spring) | Feb 25 – Mar 31 |
| Broccoli | Transplant outdoors (spring) | Apr 1 – Apr 30 |
| Broccoli | Start seeds indoors (fall) | Jun 20 – Jun 30 |
| Broccoli | Transplant outdoors (fall) | Jul 20 – Jul 31 |
| Cabbage | Start seeds indoors (spring) | Feb 15 – Mar 15 |
| Cabbage | Transplant outdoors (spring) | Mar 15 – Apr 15 |
| Cabbage | Start seeds indoors (fall) | Jun 10 – Jul 10 |
| Cabbage | Transplant outdoors (fall) | Jul 10 – Aug 10 |
| Leaf lettuce | Sow outdoors (spring) | Mar 15 – May 31 |
| Leaf lettuce | Sow outdoors (fall) | Jul 10 – Aug 26 |
| Spinach | Sow outdoors (spring) | Mar 8 – Apr 21 |
| Spinach | Sow outdoors (fall) | Jul 27 – Aug 31 |
| Radishes | Sow outdoors (spring) | Mar 15 – May 5 |
| Radishes | Sow outdoors (fall) | Jul 10 – Sep 10 |
| Kale | Sow outdoors (spring) | Apr 1 – Apr 21 |
| Kale | Sow outdoors (fall) | Jul 3 – Aug 10 |
| Carrots | Sow outdoors (spring) | Apr 15 – May 31 |
| Carrots | Sow outdoors (fall) | Jun 10 – Jul 26 |
| Garlic | Plant outdoors (fall) | Oct 10 – Nov 10 |
Where these dates come from
ZIP code 52638 is matched to the NOAA station Burlington Muni Ap, IA, 12.7 km away, at 692 ft elevation (33 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Burlington Muni Ap, IA (used) | 692 ft | Apr 15 | Oct 20 |
| Burlington 2S, IA | 690 ft | Apr 18 | Oct 20 |
| Gladstone Dam 18, IL | 538 ft | Apr 8 | Oct 29 |
| Ft Madison, IA | 530 ft | Apr 12 | Oct 25 |
Frost dates near Middletown
- Danville, IA 52623 · last Apr 15, first Oct 20
- West Burlington, IA 52655 · last Apr 15, first Oct 20
- Denmark, IA 52624 · last Apr 15, first Oct 20
- Burlington, IA 52601 · last Apr 15, first Oct 20
- Wever, IA 52658 · last Apr 12, first Oct 25
- Sperry, IA 52650 · last Apr 15, first Oct 20
- New London, IA 52645 · last Apr 30, first Oct 10
- Yarmouth, IA 52660 · last Apr 30, first Oct 10
Frequently asked questions
- When is the last frost in Middletown, IA?
- For ZIP code 52638, the average last spring frost (32°F) is April 15, based on NOAA 1991-2020 climate normals for the Burlington Muni Ap, IA weather station. There is a 1-in-10 chance of a frost after May 1.
- When is the first frost in Middletown, IA?
- The average first fall frost (32°F) is October 20. There is a 1-in-10 chance of frost by October 6, so tender plants are at risk from that point on.
- How long is the growing season in 52638?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 187 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.