USDA Hardiness Zone 5a
Frost Dates for 48625 — Harrison, Michigan
NOAA 1991–2020 normals from Houghton Lake 6 WSW, MI (1,135 ft), 18 miles north.
Updated
In Harrison, the last spring frost (32°F) is around May 30 in half of years and has passed by June 19 in nine years out of ten. The first fall frost comes around September 15, as early as August 26 one year in ten, leaving a typical freeze-free season of 106 days (NOAA, Houghton Lake 6 WSW, MI).
- Last spring frost
- May 30
- First fall frost
- September 15
- Growing season
- 106 days
- Hardiness zone
- 5a
50% probability
50% probability
freeze-free, 50%
-20 to -15°F (-28.9 to -26.1°C) coldest night
- First snow
- November 13
- Last snow
- April 12
- Winters with snow
- 100%
- Snow per year
- 66"
median, 1991–2020
median, 1991–2020
26 of 26 observed
NOAA normal
Frost risk by date in Harrison
Half of springs at Houghton Lake 6 WSW, MI see their last 32°F night by May 30; only one in ten is past it by May 12, and one in ten still has one after June 19. Planting tender crops after June 5 leaves a 30% risk of a frost on them, after June 9 20%, and after June 19 10%. The 20 days between the even-odds date and the one-in-ten date is wider than at 95% of the 172 Michigan stations behind this site's ZIP pages.
In fall the first 32°F night comes by September 15 in half of years, as early as August 26 one year in ten, and holds off past October 1 one year in ten. A hard freeze of 28°F follows 15 days later, around September 30; in spring the one-in-ten date for 28°F is May 31, 19 days before the 32°F one. The freeze-free season lasts 106 days in a typical year, shorter than at 98% of the 172 Michigan stations; it reaches 130 days one year in ten and falls short of 80 one year in ten. On average 191 nights a year drop to 32°F or below. Severe cold of 16°F or below comes every winter, usually between November 13 and April 5.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | too rare for a date | ||||||||
| 32°F | May 12 | May 19 | May 23 | May 27 | May 30 | Jun 1 | Jun 5 | Jun 9 | Jun 19 |
| 28°F | Apr 28 | May 3 | May 7 | May 11 | May 16 | May 19 | May 22 | May 27 | May 31 |
| 24°F | Apr 14 | Apr 20 | Apr 23 | Apr 26 | Apr 30 | May 2 | May 7 | May 13 | May 20 |
| 20°F | Apr 3 | Apr 7 | Apr 11 | Apr 15 | Apr 18 | Apr 21 | Apr 25 | Apr 30 | May 6 |
| 16°F | Mar 23 | Mar 29 | Apr 1 | Apr 3 | Apr 5 | Apr 8 | Apr 11 | Apr 15 | Apr 20 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | too rare for a date | ||||||||
| 32°F | Aug 26 | Sep 2 | Sep 7 | Sep 11 | Sep 15 | Sep 19 | Sep 22 | Sep 26 | Oct 1 |
| 28°F | Sep 13 | Sep 19 | Sep 23 | Sep 27 | Sep 30 | Oct 3 | Oct 6 | Oct 11 | Oct 17 |
| 24°F | Sep 26 | Oct 1 | Oct 5 | Oct 10 | Oct 13 | Oct 18 | Oct 23 | Oct 27 | Nov 1 |
| 20°F | Oct 8 | Oct 15 | Oct 22 | Oct 27 | Oct 30 | Nov 2 | Nov 6 | Nov 9 | Nov 15 |
| 16°F | Oct 29 | Nov 2 | Nov 6 | Nov 10 | Nov 13 | Nov 16 | Nov 19 | Nov 23 | Nov 29 |
Freeze probabilities 1991–2020 at Houghton Lake 6 WSW, 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 48625 →Compare Harrison with another place →
Weather by month in Harrison
July is the warmest month at Houghton Lake 6 WSW, MI, averaging 82°F by day and 53°F at night; January is the coldest at 28°F and 11°F. A freezing night is all but certain in every month from October to May (a 90% chance or more). July is the only month with under a 10% chance of a 32°F night. In spring, June still brings one in 41% of years.
Warmth for growing adds up to 1,992 growing degree days a year (base 50°F), fewer than at 78% of the 172 Michigan stations. 32% of them (637) have built up by the end of June, and July adds the most, 546. Precipitation totals 31.9 inches a year, most in May (3.6") and least in February (1.5"); May to September bring 50% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 28 | 11 | 1.8 | 100% | 30 | 0 |
| Feb | 32 | 10 | 1.5 | 100% | 28 | 0 |
| Mar | 42 | 17 | 1.7 | 100% | 29 | 3 |
| Apr | 54 | 29 | 3.1 | 100% | 21 | 35 |
| May | 68 | 40 | 3.6 | 98% | 8 | 186 |
| Jun | 78 | 50 | 3.6 | 41% | 1 | 413 |
| Jul | 82 | 53 | 2.9 | 4% | <1 | 546 |
| Aug | 80 | 51 | 3.1 | 16% | <1 | 487 |
| Sep | 72 | 43 | 2.8 | 86% | 5 | 254 |
| Oct | 59 | 34 | 3.5 | 100% | 15 | 63 |
| Nov | 44 | 26 | 2.4 | 100% | 24 | 6 |
| Dec | 34 | 18 | 1.9 | 100% | 30 | 0 |
Monthly normals 1991–2020 at Houghton Lake 6 WSW, MI (1,135 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, Gladwin, MI, 18 miles east of Harrison and 360 feet lower, has a last frost 21 days earlier (May 9), a first frost 19 days later (October 4), a season 42 days longer.
When it snows in Harrison, Michigan
The first measurable snow (0.1 inch or more) in Harrison usually arrives around November 13, and the last of the season around April 12. Those are the middle dates across the winters of 1991–2020 at Houghton Lake 6 WSW, MI, 18.1 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 48 days after the last snow.
Planting calendar for 48625
| When | What to do |
|---|---|
| March 21 – April 4 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| April 4 – April 18 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| May 2 – May 16 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 30 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by June 23 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 1 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| September 15 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 48625 is 18 miles from Houghton Lake 6 WSW, MI, which stands at 1,135 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 48625 in zone 5a, the band where the coldest night of the year averaged -20 to -15°F (-28.9 to -26.1°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.