USDA Hardiness Zone 4a
Frost Dates for 49920 — Crystal Falls, Michigan
NOAA 1991–2020 normals from Amasa 1W, MI (1,470 ft), 9 miles northwest.
Updated
In Crystal Falls, the last spring frost (32°F) is around June 6 in half of years and has passed by July 7 in nine years out of ten. The first fall frost comes around September 9, as early as August 20 one year in ten, leaving a typical freeze-free season of 94 days (NOAA, Amasa 1W, MI).
- Last spring frost
- June 6
- First fall frost
- September 9
- Growing season
- 94 days
- Hardiness zone
- 4a
50% probability
50% probability
freeze-free, 50%
-30 to -25°F (-34.4 to -31.7°C) coldest night
- First snow
- November 9
- Last snow
- April 18
- Winters with snow
- 100%
- Snow per year
- —
median, 1991–2020
median, 1991–2020
19 of 19 observed
NOAA normal
Frost risk by date in Crystal Falls
Half of springs at Amasa 1W, MI see their last 32°F night by June 6; only one in ten is past it by May 23, and one in ten still has one after July 7. Planting tender crops after June 14 leaves a 30% risk of a frost on them, after June 21 20%, and after July 7 10%. The 31 days between the even-odds date and the one-in-ten date is the widest of the 172 Michigan stations behind this site's ZIP pages, so a fixed calendar date is a gamble here.
In fall the first 32°F night comes by September 9 in half of years, as early as August 20 one year in ten, and holds off past September 27 one year in ten. A hard freeze of 28°F follows 16 days later, around September 25; in spring the one-in-ten date for 28°F is June 8, 29 days before the 32°F one. The freeze-free season lasts 94 days in a typical year, the shortest of the 172 Michigan stations; it reaches 118 days one year in ten and falls short of 59 one year in ten. On average 203 nights a year drop to 32°F or below. Severe cold of 16°F or below comes every winter, usually between November 4 and April 18.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | too rare for a date | ||||||||
| 32°F | May 23 | May 28 | May 31 | Jun 3 | Jun 6 | Jun 10 | Jun 14 | Jun 21 | Jul 7 |
| 28°F | May 6 | May 13 | May 17 | May 21 | May 24 | May 27 | May 31 | Jun 3 | Jun 8 |
| 24°F | Apr 26 | Apr 30 | May 3 | May 6 | May 9 | May 13 | May 16 | May 21 | May 27 |
| 20°F | Apr 14 | Apr 19 | Apr 23 | Apr 26 | Apr 28 | Apr 30 | May 4 | May 8 | May 16 |
| 16°F | Apr 4 | Apr 8 | Apr 12 | Apr 15 | Apr 18 | Apr 21 | Apr 24 | Apr 28 | May 2 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | too rare for a date | ||||||||
| 32°F | Aug 20 | Aug 29 | Sep 2 | Sep 5 | Sep 9 | Sep 13 | Sep 17 | Sep 21 | Sep 27 |
| 28°F | Sep 7 | Sep 14 | Sep 18 | Sep 22 | Sep 25 | Sep 29 | Oct 1 | Oct 5 | Oct 9 |
| 24°F | Sep 22 | Sep 27 | Oct 1 | Oct 4 | Oct 6 | Oct 9 | Oct 13 | Oct 18 | Oct 25 |
| 20°F | Oct 5 | Oct 10 | Oct 14 | Oct 18 | Oct 22 | Oct 26 | Oct 30 | Nov 2 | Nov 7 |
| 16°F | Oct 17 | Oct 24 | Oct 30 | Nov 1 | Nov 4 | Nov 6 | Nov 10 | Nov 14 | Nov 19 |
Freeze probabilities 1991–2020 at Amasa 1W, 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 49920 →Compare Crystal Falls with another place →
Weather by month in Crystal Falls
July is the warmest month at Amasa 1W, MI, averaging 79°F by day and 51°F at night; January is the coldest at 22°F and 0°F. A freezing night is all but certain in every month from September to May (a 90% chance or more). No month is safe from a 32°F night: even the warmest has at least a 10% chance. In spring, June still brings one in 64% of years and July still brings one in 13% of years.
Warmth for growing adds up to 1,526 growing degree days a year (base 50°F), fewer than at 98% of the 172 Michigan stations. 30% of them (455) have built up by the end of June, and July adds the most, 455.
| Month | High °F | Low °F | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|
| Jan | 22 | 0 | 100% | 31 | 0 |
| Feb | 26 | 0 | 100% | 28 | 0 |
| Mar | 37 | 10 | 100% | 29 | 3 |
| Apr | 50 | 24 | 100% | 25 | 14 |
| May | 65 | 37 | 100% | 10 | 127 |
| Jun | 74 | 46 | 64% | 1 | 312 |
| Jul | 79 | 51 | 13% | 0 | 455 |
| Aug | 76 | 49 | 24% | <1 | 386 |
| Sep | 68 | 42 | 91% | 4 | 195 |
| Oct | 54 | 31 | 100% | 18 | 33 |
| Nov | 39 | 21 | 100% | 26 | 2 |
| Dec | 27 | 8 | 100% | 31 | 0 |
Monthly normals 1991–2020 at Amasa 1W, MI (1,470 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, Stambaugh 2SSE, MI, 14 miles west of Crystal Falls, has a last frost 2 days earlier (June 4), a first frost 1 day later (September 10), a season 1 day longer.
When it snows in Crystal Falls, Michigan
The first measurable snow (0.1 inch or more) in Crystal Falls usually arrives around November 9, and the last of the season around April 18. Those are the middle dates across the winters of 1991–2020 at Amasa 1W, MI, 8.8 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 49 days after the last snow.
Planting calendar for 49920
| When | What to do |
|---|---|
| March 28 – April 11 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| April 11 – April 25 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| May 9 – May 23 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| June 6 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by June 17 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by August 26 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| September 9 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 49920 is 9 miles from Amasa 1W, MI, which stands at 1,470 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 49920 in zone 4a, the band where the coldest night of the year averaged -30 to -25°F (-34.4 to -31.7°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.