USDA Hardiness Zone 6a
Frost Dates for 49242 — Hillsdale, Michigan
NOAA 1991–2020 normals from Hillsdale, MI (1,080 ft), 3 miles north.
Updated
In Hillsdale, the last spring frost (32°F) is around May 3 in half of years and has passed by May 19 in nine years out of ten. The first fall frost comes around October 12, as early as September 29 one year in ten, leaving a typical freeze-free season of 161 days (NOAA, Hillsdale, MI).
- Last spring frost
- May 3
- First fall frost
- October 12
- Growing season
- 161 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 18
- Last snow
- April 2
- Winters with snow
- 100%
- Snow per year
- 44.1"
median, 1991–2020
median, 1991–2020
27 of 27 observed
NOAA normal
Frost risk by date in Hillsdale
Half of springs at Hillsdale, MI see their last 32°F night by May 3; only one in ten is past it by April 20, and one in ten still has one after May 19. Planting tender crops after May 10 leaves a 30% risk of a frost on them, after May 14 20%, and after May 19 10%. The 16 days between the even-odds date and the one-in-ten date is narrower than at 38% of the 172 Michigan stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 12 in half of years, as early as September 29 one year in ten, and holds off past October 27 one year in ten. A hard freeze of 28°F follows 14 days later, around October 26; in spring the one-in-ten date for 28°F is May 9, 10 days before the 32°F one. The freeze-free season lasts 161 days in a typical year, longer than at 56% of the 172 Michigan stations; it reaches 181 days one year in ten and falls short of 140 one year in ten. On average 148 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 14, and return around October 1. Severe cold of 16°F or below comes every winter, usually between November 30 and March 22.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 30 | May 3 | May 8 | May 11 | May 14 | May 18 | May 21 | May 26 | May 30 |
| 32°F | Apr 20 | Apr 24 | Apr 28 | Apr 30 | May 3 | May 6 | May 10 | May 14 | May 19 |
| 28°F | Apr 8 | Apr 13 | Apr 17 | Apr 20 | Apr 23 | Apr 27 | Apr 30 | May 3 | May 9 |
| 24°F | Mar 29 | Apr 2 | Apr 4 | Apr 8 | Apr 11 | Apr 14 | Apr 18 | Apr 21 | Apr 30 |
| 20°F | Mar 16 | Mar 22 | Mar 26 | Mar 30 | Apr 1 | Apr 3 | Apr 6 | Apr 11 | Apr 17 |
| 16°F | Mar 6 | Mar 12 | Mar 15 | Mar 19 | Mar 22 | Mar 26 | Mar 30 | Apr 1 | Apr 6 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 18 | Sep 23 | Sep 27 | Sep 30 | Oct 1 | Oct 4 | Oct 6 | Oct 9 | Oct 13 |
| 32°F | Sep 29 | Oct 3 | Oct 6 | Oct 10 | Oct 12 | Oct 15 | Oct 19 | Oct 22 | Oct 27 |
| 28°F | Oct 10 | Oct 16 | Oct 20 | Oct 23 | Oct 26 | Oct 28 | Oct 31 | Nov 3 | Nov 8 |
| 24°F | Oct 24 | Oct 29 | Nov 1 | Nov 3 | Nov 5 | Nov 8 | Nov 12 | Nov 15 | Nov 20 |
| 20°F | Nov 3 | Nov 7 | Nov 10 | Nov 14 | Nov 17 | Nov 20 | Nov 25 | Nov 30 | Dec 6 |
| 16°F | Nov 12 | Nov 17 | Nov 21 | Nov 26 | Nov 30 | Dec 3 | Dec 6 | Dec 12 | Dec 18 |
Freeze probabilities 1991–2020 at Hillsdale, 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 49242 →Compare Hillsdale with another place →
Frost risk through the year in Hillsdale
In Hillsdale, the spring curve drops under 10% on May 19 and the fall curve passes 10% on September 29, 133 days later; that gap is longer than at 59% of the 172 Michigan stations with frost dates. The spring risk falls from 90% to 10% over 29 days (April 20 to May 19) and the fall risk climbs from 10% to 90% over 28 days (September 29 to October 27): both ends of the season vary about as much. At Coldwater St School, MI, 19 miles west, the same gap runs from May 18 to September 30, 2 days longer.
| Planted on | Another 32°F night | 28°F night |
|---|---|---|
| Apr 19 | over 90% | 63% |
| Apr 26 | 75% | 43% |
| May 350% date | 50% | 20% |
| May 10 | 30% | under 10% |
| May 17 | 14% | under 10% |
| May 24 | under 10% | under 10% |
Weather by month in Hillsdale
July is the warmest month at Hillsdale, MI, averaging 83°F by day and 60°F at night; January is the coldest at 31°F and 15°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 60% of years.
Warmth for growing adds up to 2,649 growing degree days a year (base 50°F), more than at 66% of the 172 Michigan stations. 34% of them (890) have built up by the end of June, and July adds the most, 657. Precipitation totals 39.6 inches a year, most in May (4.6") and least in February (2.3"); May to September bring 49% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 31 | 15 | 2.8 | 100% | 29 | 0 |
| Feb | 34 | 16 | 2.3 | 100% | 26 | 1 |
| Mar | 44 | 25 | 2.4 | 100% | 24 | 14 |
| Apr | 58 | 35 | 3.7 | 100% | 13 | 73 |
| May | 69 | 47 | 4.6 | 60% | 2 | 276 |
| Jun | 79 | 57 | 3.9 | 0% | 0 | 526 |
| Jul | 83 | 60 | 3.6 | 0% | 0 | 657 |
| Aug | 80 | 58 | 3.9 | 0% | 0 | 595 |
| Sep | 74 | 50 | 3.6 | 12% | 1 | 370 |
| Oct | 61 | 40 | 3.4 | 95% | 7 | 118 |
| Nov | 47 | 30 | 3.0 | 100% | 19 | 18 |
| Dec | 36 | 22 | 2.4 | 100% | 27 | 2 |
Monthly normals 1991–2020 at Hillsdale, MI (1,080 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, Coldwater St School, MI, 19 miles west of Hillsdale, has a last frost 1 day earlier (May 2), a first frost 1 day later (October 13), a season 2 days longer.
When it snows in Hillsdale, Michigan
The first measurable snow (0.1 inch or more) in Hillsdale usually arrives around November 18, and the last of the season around April 2. Those are the middle dates across the winters of 1991–2020 at Hillsdale, MI, 2.6 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 31 days after the last snow.
Planting calendar for 49242
| When | What to do |
|---|---|
| February 22 – March 8 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 8 – March 22 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 5 – April 19 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 3 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 20 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 28 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 12 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 49242 is 3 miles from Hillsdale, MI, which stands at 1,080 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 7 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 49242 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.