Iowa frost dates
Across Iowa, the average last spring frost is around April 25 and the average first fall frost around October 8 - roughly 166 frost-free days. USDA zones 4b, 5a, 5b.
What these dates mean for planting in Iowa
Counted from the average frost dates above. For every crop, see the full Iowa planting calendar.
Frost dates by zone in Iowa
Iowa spans USDA zones 4b, 5a, 5b. Colder zones - usually higher or further inland - have later spring and earlier fall frosts than the state average.
Frost dates in nearby states
Questions gardeners ask
When is the last frost in Iowa?
The statewide average last spring frost is around April 25. There is still roughly a one-in-two chance of frost on that date, so for tender plants a safer date is about two weeks later, around May 9.
When is the first frost in Iowa?
The average first fall frost is around October 8. Frost-tender crops such as tomatoes, peppers, beans and squash should be harvested or covered before then; an early frost two weeks sooner, around September 24, happens in roughly one year in ten.
How long is the growing season in Iowa?
About 166 frost-free days on average between the last spring frost and the first fall frost. That is enough for most vegetables, including a fall crop of greens and roots.
When can I plant tomatoes outside in Iowa?
Plant tomato transplants outdoors between April 25 – May 12, once nights stay above about 50°F. Start seeds indoors six to eight weeks earlier.
Is it safe to plant on the average last frost date?
For hardy crops such as peas, spinach, onions and cabbage, yes - they handle a light frost. For tender crops, no: the average date still carries about a 50% chance of a later frost, so wait one to two weeks or keep row cover ready.
→ Turn these into sowing dates with the Iowa planting calendar, look up an exact ZIP code, or read how frost dates work. Month by month: what to plant in January · what to plant in February · what to plant in March · what to plant in April · what to plant in May · what to plant in June · what to plant in July · what to plant in August · what to plant in September · what to plant in October · what to plant in November.
Statewide average from NOAA/NCEI freeze normals. Cautious and gambler dates are about two weeks either side of the average.