USDA Hardiness Zone 6a
Frost Dates for 49302 — Alto, Michigan
NOAA 1991–2020 normals from Nwsfo Grand Rapids, MI (775 ft), 8 miles northwest.
Updated
In Alto, the last spring frost (32°F) is around April 30 in half of years and has passed by May 17 in nine years out of ten. The first fall frost comes around October 14, as early as October 1 one year in ten, leaving a typical freeze-free season of 167 days (NOAA, Nwsfo Grand Rapids, MI).
- Last spring frost
- April 30
- First fall frost
- October 14
- Growing season
- 167 days
- Hardiness zone
- 6a
50% probability
50% probability
freeze-free, 50%
-10 to -5°F (-23.3 to -20.6°C) coldest night
- First snow
- November 9
- Last snow
- April 13
- Winters with snow
- 100%
- Snow per year
- 77.6"
median, 1991–2020
median, 1991–2020
30 of 30 observed
NOAA normal
Frost risk by date in Alto
Half of springs at Nwsfo Grand Rapids, MI see their last 32°F night by April 30; only one in ten is past it by April 16, and one in ten still has one after May 17. Planting tender crops after May 7 leaves a 30% risk of a frost on them, after May 11 20%, and after May 17 10%. The 17 days between the even-odds date and the one-in-ten date is wider than at 62% of the 172 Michigan stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 14 in half of years, as early as October 1 one year in ten, and holds off past October 28 one year in ten. A hard freeze of 28°F follows 12 days later, around October 26; in spring the one-in-ten date for 28°F is May 5, 12 days before the 32°F one. The freeze-free season lasts 167 days in a typical year, longer than at 73% of the 172 Michigan stations; it reaches 187 days one year in ten and falls short of 146 one year in ten. On average 140 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 11 days longer, to about May 11, and return around October 3. Severe cold of 16°F or below comes every winter, usually between December 7 and March 18.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 27 | May 1 | May 5 | May 8 | May 11 | May 15 | May 19 | May 22 | May 27 |
| 32°F | Apr 16 | Apr 20 | Apr 24 | Apr 28 | Apr 30 | May 4 | May 7 | May 11 | May 17 |
| 28°F | Apr 4 | Apr 8 | Apr 12 | Apr 15 | Apr 18 | Apr 21 | Apr 25 | Apr 30 | May 5 |
| 24°F | Mar 23 | Mar 29 | Mar 31 | Apr 3 | Apr 5 | Apr 8 | Apr 12 | Apr 16 | Apr 21 |
| 20°F | Mar 13 | Mar 18 | Mar 21 | Mar 25 | Mar 28 | Mar 31 | Apr 2 | Apr 5 | Apr 10 |
| 16°F | Feb 28 | Mar 7 | Mar 12 | Mar 15 | Mar 18 | Mar 20 | Mar 24 | Mar 28 | Apr 1 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 21 | Sep 25 | Sep 28 | Oct 1 | Oct 3 | Oct 5 | Oct 7 | Oct 10 | Oct 14 |
| 32°F | Oct 1 | Oct 5 | Oct 8 | Oct 11 | Oct 14 | Oct 16 | Oct 19 | Oct 22 | Oct 28 |
| 28°F | Oct 11 | Oct 16 | Oct 20 | Oct 23 | Oct 26 | Oct 30 | Nov 2 | Nov 6 | Nov 11 |
| 24°F | Oct 25 | Nov 1 | Nov 3 | Nov 7 | Nov 11 | Nov 16 | Nov 21 | Nov 26 | Dec 1 |
| 20°F | Nov 8 | Nov 15 | Nov 20 | Nov 25 | Nov 27 | Dec 1 | Dec 3 | Dec 7 | Dec 14 |
| 16°F | Nov 22 | Nov 28 | Dec 1 | Dec 4 | Dec 7 | Dec 10 | Dec 14 | Dec 19 | Dec 23 |
Freeze probabilities 1991–2020 at Nwsfo Grand Rapids, MI, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 49302 →Compare Alto with another place →
Compared with the next station
The nearest other station, Grand Rapids, MI, 8 miles northwest of Alto, has a last frost 1 day earlier (April 29), a first frost 6 days later (October 20), a season 7 days longer.
When it snows in Alto, Michigan
The first measurable snow (0.1 inch or more) in Alto usually arrives around November 9, and the last of the season around April 13. Those are the middle dates across the winters of 1991–2020 at Grand Rapids, MI, 7.6 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 17 days after the last snow.
Planting calendar for 49302
| When | What to do |
|---|---|
| February 19 – March 5 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 5 – March 19 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 2 – April 16 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 30 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 22 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 30 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 14 onward | Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter. |
The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.
Where these figures come from
ZIP 49302 is 8 miles from Nwsfo Grand Rapids, MI, which stands at 775 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station; its figures are presented in full for 49316 (Caledonia). The 2023 USDA Plant Hardiness Zone Map lists ZIP 49302 in zone 6a, the band where the coldest night of the year averaged -10 to -5°F (-23.3 to -20.6°C) over 1991–2020; a zone describes winter lows, not frost dates.
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.