Frost Dates for Iowa City, IA
In Iowa City, IA, the average last spring frost is around Apr 21 and the average first fall frost around Oct 18, for a growing season of about 180 days. For frost-tender plants, wait until May 6, when the chance of frost drops to 10%.
Based on NOAA 1991–2020 records from the Iowa City Muni Airport, IA weather station, 2 miles away, elevation 650 ft. Frost can come earlier in low spots and valleys and later near cities and large lakes.
Frost probability by date
Chance of a 32°F frost after the spring date, or before the fall date.
| Chance | Last spring frost | First fall frost |
|---|---|---|
| 10% | May 6 | Oct 4 |
| 20% | May 1 | Oct 10 |
| 30% | Apr 28 | Oct 13 |
| 40% | Apr 24 | Oct 16 |
| 50% | Apr 21 | Oct 18 |
| 60% | Apr 18 | Oct 20 |
| 70% | Apr 14 | Oct 23 |
| 80% | Apr 10 | Oct 26 |
| 90% | Apr 5 | Oct 31 |
Light frost vs. hard freeze
Average (50%) dates for each temperature. Tender plants are damaged at 36°F; most hardy crops survive until 28°F.
| Temperature | Last in spring | First in fall |
|---|---|---|
| Light frost (36°F) | May 1 | Oct 9 |
| Frost / freeze (32°F) | Apr 21 | Oct 18 |
| Hard freeze (28°F) | Apr 9 | Oct 28 |
Planting calendar for Iowa City
Transplant Apr 28 – May 12
Transplant May 5 – May 19
Transplant May 5 – May 19
Transplant Apr 28 – May 12
Sow or transplant Apr 28 – May 12
Sow or transplant Apr 28 – May 12
Sow or transplant May 5 – May 19
Sow or transplant Mar 24 – Apr 7
Fall sowing Aug 23 – Sep 20
Fall sowing Aug 23 – Sep 13
Fall sowing Aug 9 – Aug 23
Sow or transplant Mar 24 – Apr 7
Fall sowing Aug 9 – Sep 6
Transplant Apr 7 – Apr 21
Fall sowing Jul 26 – Aug 9
Transplant Mar 31 – Apr 14
Fall sowing Jul 26 – Aug 9
Fall sowing Jul 26 – Aug 9
Fall sowing Sep 6 – Sep 27
Fall sowing Aug 9 – Aug 23
Plant Mar 24 – Apr 7
Based on the average last frost (Apr 21) and first frost (Oct 18). The dashed lines mark those dates. Seed packets list days to maturity; adjust for your varieties.