Frost Dates for Waterloo, IA
In Waterloo, IA, the average last spring frost is around Apr 27 and the average first fall frost around Oct 10, for a growing season of about 165 days. For frost-tender plants, wait until May 10, when the chance of frost drops to 10%.
Based on NOAA 1991–2020 records from the Waterloo Muni Airport, IA weather station, 5 miles away, elevation 868 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 10 | Sep 26 |
| 20% | May 5 | Oct 1 |
| 30% | May 2 | Oct 4 |
| 40% | Apr 30 | Oct 7 |
| 50% | Apr 27 | Oct 10 |
| 60% | Apr 24 | Oct 12 |
| 70% | Apr 20 | Oct 15 |
| 80% | Apr 16 | Oct 18 |
| 90% | Apr 11 | 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 6 | Sep 30 |
| Frost / freeze (32°F) | Apr 27 | Oct 10 |
| Hard freeze (28°F) | Apr 16 | Oct 20 |
Planting calendar for Waterloo
Transplant May 4 – May 18
Transplant May 11 – May 25
Transplant May 11 – May 25
Transplant May 4 – May 18
Sow or transplant May 4 – May 18
Sow or transplant May 4 – May 18
Sow or transplant May 11 – May 25
Sow or transplant Mar 30 – Apr 13
Fall sowing Aug 15 – Sep 12
Fall sowing Aug 15 – Sep 5
Fall sowing Aug 1 – Aug 15
Sow or transplant Mar 30 – Apr 13
Fall sowing Aug 1 – Aug 29
Transplant Apr 13 – Apr 27
Fall sowing Jul 18 – Aug 1
Transplant Apr 6 – Apr 20
Fall sowing Jul 18 – Aug 1
Fall sowing Jul 18 – Aug 1
Fall sowing Aug 29 – Sep 19
Fall sowing Aug 1 – Aug 15
Plant Mar 30 – Apr 13
Based on the average last frost (Apr 27) and first frost (Oct 10). The dashed lines mark those dates. Seed packets list days to maturity; adjust for your varieties.