Castalia, IA 52133 Frost Dates
When can you plant in Castalia, IA?
Around 05/03 is the usual last spring frost, about 248 days away. The first fall frost typically arrives around 10/07, about 157 frost-free days later.
Castalia sits in USDA Zone 5a (-20 to -15°F average annual minimum). The dates above are NOAA's 1991-2020 normal at the nearest reporting station, a 30-year average, not a forecast.
What to do before the first frost
About 6 weeks of growing season left in Castalia before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
The actual range around Castalia's last frost
05/03 is the middle of 30 years of NOAA records, not a promise. Plant by 04/19 and you're betting against frost in roughly 9 years out of 10. 05/16 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Castalia compares
At roughly 157 frost-free days, Castalia places 33,460 of 40,283 ZIP codes in this dataset. Within IA, it ranks 855 of 1,042.
Learn more
zone vs. frost date covers why Zone 5a and Castalia's frost date answer different questions. the frost range covers how to read the range around Castalia's dates instead of trusting one.