Frost dates for 52243Iowa City, IA
The average last spring frost in Iowa City is April 21 and the average first fall frost is October 18, giving a typical growing season of about 180 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 21
- Average first fall frost
- Oct 18
- Growing season
- 180 days
Safer after May 6 (1-in-10 risk)
Possible by Oct 4 (1-in-10 risk)
Last frost typically in 176 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 17 · May 1 · May 15 | Sep 26 · Oct 9 · Oct 21 | 161 days | 100% |
| Frost / freeze (32°F) | Apr 5 · Apr 21 · May 6 | Oct 4 · Oct 18 · Oct 31 | 180 days | 100% |
| Hard freeze (28°F) | Mar 25 · Apr 9 · Apr 27 | Oct 15 · Oct 28 · Nov 9 | 202 days | 100% |
Planting calendar for Iowa City
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 21 – May 27 |
| Tomatoes | Transplant outdoors | May 7 – Jun 28 |
| Peppers | Start seeds indoors | Mar 21 – Apr 21 |
| Peppers | Transplant outdoors | May 21 – Jun 21 |
| Eggplant | Start seeds indoors | Apr 7 – May 6 |
| Eggplant | Transplant outdoors | May 21 – Jun 21 |
| Cucumbers | Sow outdoors | May 21 – Jul 8 |
| Summer squash | Sow outdoors | May 7 – Jun 21 |
| Winter squash & pumpkins | Sow outdoors | May 21 – Jun 21 |
| Snap beans | Sow outdoors | May 7 – Jul 31 |
| Sweet corn | Sow outdoors | May 7 – Jun 28 |
| Watermelon & cantaloupe | Sow outdoors | May 21 – Jun 21 |
| Okra | Sow outdoors | May 14 – Jun 6 |
| Peas | Sow outdoors (spring) | Mar 21 – May 6 |
| Potatoes | Plant outdoors (spring) | Mar 21 – May 21 |
| Onions | Start seeds indoors (spring) | Feb 7 – Mar 6 |
| Onions | Transplant outdoors (spring) | Apr 7 – May 6 |
| Broccoli | Start seeds indoors (spring) | Mar 3 – Apr 6 |
| Broccoli | Transplant outdoors (spring) | Apr 7 – May 6 |
| Broccoli | Start seeds indoors (fall) | Jun 18 – Jun 28 |
| Broccoli | Transplant outdoors (fall) | Jul 18 – Jul 29 |
| Cabbage | Start seeds indoors (spring) | Feb 21 – Mar 21 |
| Cabbage | Transplant outdoors (spring) | Mar 21 – Apr 21 |
| Cabbage | Start seeds indoors (fall) | Jun 8 – Jul 8 |
| Cabbage | Transplant outdoors (fall) | Jul 8 – Aug 8 |
| Leaf lettuce | Sow outdoors (spring) | Mar 21 – Jun 6 |
| Leaf lettuce | Sow outdoors (fall) | Jul 8 – Aug 24 |
| Spinach | Sow outdoors (spring) | Mar 14 – Apr 27 |
| Spinach | Sow outdoors (fall) | Jul 25 – Aug 29 |
| Radishes | Sow outdoors (spring) | Mar 21 – May 11 |
| Radishes | Sow outdoors (fall) | Jul 8 – Sep 8 |
| Kale | Sow outdoors (spring) | Apr 7 – Apr 27 |
| Kale | Sow outdoors (fall) | Jul 1 – Aug 8 |
| Carrots | Sow outdoors (spring) | Apr 21 – Jun 6 |
| Carrots | Sow outdoors (fall) | Jun 8 – Jul 24 |
| Garlic | Plant outdoors (fall) | Oct 8 – Nov 8 |
Where these dates come from
ZIP code 52243 is matched to the NOAA station Iowa City Muni Ap, IA, 3.3 km away, at 650 ft elevation (16 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Iowa City Muni Ap, IA (used) | 650 ft | Apr 21 | Oct 18 |
| Iowa City, IA | 640 ft | Apr 29 | Oct 9 |
| Cedar Rapids Muni Ap, IA | 868 ft | Apr 27 | Oct 11 |
| Tipton, IA | 820 ft | Apr 21 | Oct 15 |
Frost dates near Iowa City
- Iowa City, IA 52245 · last Apr 21, first Oct 18
- Coralville, IA 52241 · last Apr 21, first Oct 18
- North Liberty, IA 52317 · last Apr 21, first Oct 18
- Hills, IA 52235 · last Apr 29, first Oct 9
- Tiffin, IA 52340 · last Apr 21, first Oct 18
- Solon, IA 52333 · last Apr 21, first Oct 18
- West Branch, IA 52358 · last Apr 21, first Oct 15
- Lone Tree, IA 52755 · last Apr 29, first Oct 9
Frequently asked questions
- When is the last frost in Iowa City, IA?
- For ZIP code 52243, the average last spring frost (32°F) is April 21, based on NOAA 1991-2020 climate normals for the Iowa City Muni Ap, IA weather station. There is a 1-in-10 chance of a frost after May 6.
- When is the first frost in Iowa City, IA?
- The average first fall frost (32°F) is October 18. There is a 1-in-10 chance of frost by October 4, so tender plants are at risk from that point on.
- How long is the growing season in 52243?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 180 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.