Frost Dates for Marshalltown, IA
In Marshalltown, IA, the average last spring frost is around Apr 28 and the average first fall frost around Oct 7, for a growing season of about 162 days. For frost-tender plants, wait until May 11, when the chance of frost drops to 10%.
Based on NOAA 1991–2020 records from the Marshalltown, IA weather station, 2 miles away, elevation 870 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 11 | Sep 22 |
| 20% | May 6 | Sep 27 |
| 30% | May 3 | Oct 1 |
| 40% | Apr 30 | Oct 4 |
| 50% | Apr 28 | Oct 7 |
| 60% | Apr 25 | Oct 10 |
| 70% | Apr 22 | Oct 13 |
| 80% | Apr 18 | Oct 17 |
| 90% | Apr 13 | Oct 21 |
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 7 | Sep 28 |
| Frost / freeze (32°F) | Apr 28 | Oct 7 |
| Hard freeze (28°F) | Apr 17 | Oct 18 |
Planting calendar for Marshalltown
Transplant May 5 – May 19
Transplant May 12 – May 26
Transplant May 12 – May 26
Transplant May 5 – May 19
Sow or transplant May 5 – May 19
Sow or transplant May 5 – May 19
Sow or transplant May 12 – May 26
Sow or transplant Mar 31 – Apr 14
Fall sowing Aug 12 – Sep 9
Fall sowing Aug 12 – Sep 2
Fall sowing Jul 29 – Aug 12
Sow or transplant Mar 31 – Apr 14
Fall sowing Jul 29 – Aug 26
Transplant Apr 14 – Apr 28
Fall sowing Jul 15 – Jul 29
Transplant Apr 7 – Apr 21
Fall sowing Jul 15 – Jul 29
Fall sowing Jul 15 – Jul 29
Fall sowing Aug 26 – Sep 16
Fall sowing Jul 29 – Aug 12
Plant Mar 31 – Apr 14
Based on the average last frost (Apr 28) and first frost (Oct 7). The dashed lines mark those dates. Seed packets list days to maturity; adjust for your varieties.