USDA Hardiness Zone 4b
Frost Dates for 55972 — Saint Charles, Minnesota
Averages from Minnesota City Dam 5, Mn US, the nearest reporting station, 17.7 miles away.
Plant tender crops after April 23, and expect the first autumn freeze around October 16. That leaves about 175 frost-free days.
- Last spring frost
- April 23
- First fall frost
- October 16
- Growing season
- 175 days
- Hardiness zone
- 4b
50% probability
50% probability
frost-free
-25 to -20°F annual low
Planting calendar for 55972
| When | What to do |
|---|---|
| February 12 – February 26 | Start peppers and aubergines indoors They need eight to ten weeks under lights before they can go out. |
| February 26 – March 12 | Start tomatoes indoors Six to eight weeks gives a transplant big enough to set fruit early. |
| March 26 – April 9 | Sow peas, spinach, lettuce, radish outdoors These tolerate light frost and prefer to germinate in cool soil. |
| April 23 onward | Transplant tomatoes, peppers, basil, squash, cucumbers The average last freeze has passed — still watch the actual forecast. |
| by July 24 | Sow the autumn crop of carrots, beets and brassicas They need about twelve weeks to size up before growth stops. |
| by October 2 | Harvest tender crops, or be ready to cover them A first freeze two weeks early is well within normal variation. |
| October 16 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 23 to put tender plants — tomatoes, peppers, basil, squash — in the ground. That is the date by which half of years in Saint Charles, Minnesota are past their last freeze. Harvest before October 16, which leaves roughly 175 frost-free days.
ZIP 55972 sits in USDA hardiness zone 4b, meaning the average coldest night of the year falls between -25 to -20°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.