USDA Hardiness Zone 5b
Frost Dates for 50228 — Prairie City, Iowa
Averages from Des Moines 17 E, Ia US, the nearest reporting station, 3 miles away.
Plant tender crops after April 21, and expect the first autumn freeze around October 15. That leaves about 174 frost-free days.
- Last spring frost
- April 21
- First fall frost
- October 15
- Growing season
- 174 days
- Hardiness zone
- 5b
50% probability
50% probability
frost-free
-15 to -10°F annual low
Planting calendar for 50228
| When | What to do |
|---|---|
| February 10 – February 24 | Start peppers and aubergines indoors They need eight to ten weeks under lights before they can go out. |
| February 24 – March 10 | Start tomatoes indoors Six to eight weeks gives a transplant big enough to set fruit early. |
| March 24 – April 7 | Sow peas, spinach, lettuce, radish outdoors These tolerate light frost and prefer to germinate in cool soil. |
| April 21 onward | Transplant tomatoes, peppers, basil, squash, cucumbers The average last freeze has passed — still watch the actual forecast. |
| by July 23 | Sow the autumn crop of carrots, beets and brassicas They need about twelve weeks to size up before growth stops. |
| by October 1 | Harvest tender crops, or be ready to cover them A first freeze two weeks early is well within normal variation. |
| October 15 onward | Plant garlic, mulch beds, lift tender bulbs Garlic wants a cold spell; bare soil loses structure over winter. |
What these dates mean
Wait until after April 21 to put tender plants — tomatoes, peppers, basil, squash — in the ground. That is the date by which half of years in Prairie City, Iowa are past their last freeze. Harvest before October 15, which leaves roughly 174 frost-free days.
ZIP 50228 sits in USDA hardiness zone 5b, meaning the average coldest night of the year falls between -15 to -10°F. Zone decides what survives the winter; frost dates decide when to plant each spring. They are different questions, and a plant can pass one and fail the other.
These are thirty-year NOAA averages for 1991–2020, not a forecast. Any individual year can frost two to three weeks either side of these dates, so check the actual forecast before planting out.