USDA Hardiness Zone 6a
Frost Dates for 48467 — Port Austin, Michigan
NOAA 1991–2020 normals from Port Austin Wwtp, MI (605 ft), 2 miles northeast.
Updated
In Port Austin, the last spring frost (32°F) is around May 4 in half of years and has passed by May 19 in nine years out of ten. The first fall frost comes around October 26, as early as October 7 one year in ten, leaving a typical freeze-free season of 172 days (NOAA, Port Austin Wwtp, MI).
- Last spring frost
- May 4
- First fall frost
- October 26
- Growing season
- 172 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 22
- Last snow
- April 12
- Winters with snow
- 100%
- Snow per year
- —
median, 1991–2020
median, 1991–2020
16 of 16 observed
NOAA normal
Frost risk by date in Port Austin
Half of springs at Port Austin Wwtp, MI see their last 32°F night by May 4; 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 15 days between the even-odds date and the one-in-ten date is narrower than at 55% of the 172 Michigan stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 26 in half of years, as early as October 7 one year in ten, and holds off past November 8 one year in ten. A hard freeze of 28°F follows 12 days later, around November 7; in spring the one-in-ten date for 28°F is May 5, 14 days before the 32°F one. The freeze-free season lasts 172 days in a typical year, longer than at 80% of the 172 Michigan stations; it reaches 191 days one year in ten and falls short of 150 one year in ten. On average 145 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 12 days longer, to about May 16, and return around October 9. Severe cold of 16°F or below comes every winter, usually between December 10 and March 19.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 1 | May 6 | May 9 | May 12 | May 16 | May 18 | May 22 | May 25 | May 31 |
| 32°F | Apr 20 | Apr 25 | Apr 28 | May 1 | May 4 | May 7 | May 10 | May 14 | May 19 |
| 28°F | Apr 8 | Apr 13 | Apr 17 | Apr 19 | Apr 21 | Apr 24 | Apr 27 | May 1 | May 5 |
| 24°F | Mar 27 | Apr 1 | Apr 3 | Apr 6 | Apr 9 | Apr 13 | Apr 16 | Apr 18 | Apr 23 |
| 20°F | Mar 14 | Mar 20 | Mar 24 | Mar 28 | Mar 31 | Apr 2 | Apr 4 | Apr 7 | Apr 12 |
| 16°F | Mar 5 | Mar 10 | Mar 13 | Mar 16 | Mar 19 | Mar 21 | Mar 25 | Mar 29 | Apr 1 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 26 | Sep 30 | Oct 3 | Oct 6 | Oct 9 | Oct 13 | Oct 16 | Oct 21 | Oct 26 |
| 32°F | Oct 7 | Oct 14 | Oct 19 | Oct 23 | Oct 26 | Oct 29 | Nov 1 | Nov 3 | Nov 8 |
| 28°F | Oct 25 | Oct 30 | Nov 1 | Nov 4 | Nov 7 | Nov 10 | Nov 12 | Nov 16 | Nov 21 |
| 24°F | Nov 3 | Nov 8 | Nov 12 | Nov 16 | Nov 19 | Nov 22 | Nov 25 | Nov 28 | Dec 3 |
| 20°F | Nov 15 | Nov 20 | Nov 23 | Nov 26 | Nov 29 | Dec 2 | Dec 5 | Dec 10 | Dec 17 |
| 16°F | Nov 24 | Nov 29 | Dec 3 | Dec 6 | Dec 10 | Dec 14 | Dec 18 | Dec 22 | Dec 27 |
Freeze probabilities 1991–2020 at Port Austin Wwtp, 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 48467 →Compare Port Austin with another place →
Weather by month in Port Austin
July is the warmest month at Port Austin Wwtp, MI, averaging 78°F by day and 60°F at night; February is the coldest at 30°F and 15°F. A freezing night is all but certain in every month from November to April (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 62% of years.
Warmth for growing adds up to 2,214 growing degree days a year (base 50°F), fewer than at 63% of the 172 Michigan stations. 28% of them (631) have built up by the end of June, and July adds the most, 587.
| Month | High °F | Low °F | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|
| Jan | 29 | 17 | 100% | 29 | 0 |
| Feb | 30 | 15 | 100% | 27 | 0 |
| Mar | 38 | 23 | 100% | 26 | 6 |
| Apr | 51 | 33 | 100% | 14 | 32 |
| May | 64 | 44 | 62% | 1 | 179 |
| Jun | 73 | 54 | 1% | 0 | 413 |
| Jul | 78 | 60 | 0% | 0 | 587 |
| Aug | 77 | 59 | 0% | 0 | 549 |
| Sep | 71 | 52 | 4% | 0 | 335 |
| Oct | 58 | 42 | 67% | 3 | 101 |
| Nov | 45 | 32 | 100% | 17 | 12 |
| Dec | 35 | 23 | 100% | 28 | 0 |
Monthly normals 1991–2020 at Port Austin Wwtp, MI (605 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, Filion 5NNW, MI, 8 miles southwest of Port Austin, has a last frost 4 days later (May 8), a first frost 9 days earlier (October 17), a season 10 days shorter.
When it snows in Port Austin, Michigan
The first measurable snow (0.1 inch or more) in Port Austin usually arrives around November 22, and the last of the season around April 12. Those are the middle dates across the winters of 1991–2020 at Filion 5NNW, MI, 8.4 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 22 days after the last snow.
Planting calendar for 48467
| When | What to do |
|---|---|
| February 23 – March 9 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 9 – March 23 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 6 – April 20 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 4 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by August 3 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 12 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 26 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 48467 is 2 miles from Port Austin Wwtp, MI, which stands at 605 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 48467 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.