USDA Hardiness Zone 5a
Frost Dates for 48625 — Harrison, Michigan
Averages from Houghton Lake 6 Wsw, Mi US, the nearest reporting station, 18.1 miles away.
Plant tender crops after May 30, and expect the first autumn freeze around September 15. That leaves about 106 frost-free days.
- Last spring frost
- May 30
- First fall frost
- September 15
- Growing season
- 106 days
- Hardiness zone
- 5a
50% probability
50% probability
frost-free
-20 to -15°F annual low
Planting calendar for 48625
| When | What to do |
|---|---|
| March 21 – April 4 | Start peppers and aubergines indoors They need eight to ten weeks under lights before they can go out. |
| April 4 – April 18 | Start tomatoes indoors Six to eight weeks gives a transplant big enough to set fruit early. |
| May 2 – May 16 | Sow peas, spinach, lettuce, radish outdoors These tolerate light frost and prefer to germinate in cool soil. |
| May 30 onward | Transplant tomatoes, peppers, basil, squash, cucumbers The average last freeze has passed — still watch the actual forecast. |
| by June 23 | Sow the autumn crop of carrots, beets and brassicas They need about twelve weeks to size up before growth stops. |
| by September 1 | Harvest tender crops, or be ready to cover them A first freeze two weeks early is well within normal variation. |
| September 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 May 30 to put tender plants — tomatoes, peppers, basil, squash — in the ground. That is the date by which half of years in Harrison, Michigan are past their last freeze. Harvest before September 15, which leaves roughly 106 frost-free days.
ZIP 48625 sits in USDA hardiness zone 5a, meaning the average coldest night of the year falls between -20 to -15°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.