USDA Hardiness Zone 6b
Frost Dates for 48138 — Grosse Ile, Michigan
Averages from Detroit Metro Ap, Mi US, the nearest reporting station, 11.2 miles away.
Plant tender crops after April 20, and expect the first autumn freeze around October 27. That leaves about 188 frost-free days.
- Last spring frost
- April 20
- First fall frost
- October 27
- Growing season
- 188 days
- Hardiness zone
- 6b
50% probability
50% probability
frost-free
-5 to 0°F annual low
- First snow
- November 20
- Last snow
- April 15
- Winters with snow
- 100%
- Snow per year
- 53.5"
median, 1991–2020
median, 1991–2020
15 of 15 observed
NOAA normal
When it snows in Grosse Ile, Michigan
The first measurable snow (0.1 inch or more) in Grosse Ile, Michigan usually arrives around November 20, and the last of the season around April 15. Those are the middle dates across the winters of 1991–2020 at Wyandotte, Mi US, 5.4 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow.
For a gardener, snow matters less than frost: a light snow on frozen ground changes nothing, while a hard frost on an unprotected bed ends the season. Use the frost dates above for planting and the snow dates for getting hoses drained, mulch down and tender pots indoors.
Planting calendar for 48138
| When | What to do |
|---|---|
| February 9 – February 23 | Start peppers and aubergines indoors They need eight to ten weeks under lights before they can go out. |
| February 23 – March 9 | Start tomatoes indoors Six to eight weeks gives a transplant big enough to set fruit early. |
| March 23 – April 6 | Sow peas, spinach, lettuce, radish outdoors These tolerate light frost and prefer to germinate in cool soil. |
| April 20 onward | Transplant tomatoes, peppers, basil, squash, cucumbers The average last freeze has passed — still watch the actual forecast. |
| by August 4 | Sow the autumn crop of carrots, beets and brassicas They need about twelve weeks to size up before growth stops. |
| by October 13 | Harvest tender crops, or be ready to cover them A first freeze two weeks early is well within normal variation. |
| October 27 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 20 to put tender plants — tomatoes, peppers, basil, squash — in the ground. That is the date by which half of years in Grosse Ile, Michigan are past their last freeze. Harvest before October 27, which leaves roughly 188 frost-free days.
ZIP 48138 sits in USDA hardiness zone 6b, meaning the average coldest night of the year falls between -5 to 0°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.