USDA Hardiness Zone 4b
Frost Dates for 49911 — Bessemer, Michigan
NOAA 1991–2020 normals from Ironwood #2, MI (1,520 ft), 4 miles west.
Updated
In Bessemer, the last spring frost (32°F) is around May 19 in half of years and has passed by June 3 in nine years out of ten. The first fall frost comes around September 28, as early as September 12 one year in ten, leaving a typical freeze-free season of 130 days (NOAA, Ironwood #2, MI).
- Last spring frost
- May 19
- First fall frost
- September 28
- Growing season
- 130 days
- Hardiness zone
- 4b
50% probability
50% probability
freeze-free, 50%
-25 to -20°F (-31.7 to -28.9°C) coldest night
- First snow
- October 19
- Last snow
- April 29
- Winters with snow
- 100%
- Snow per year
- 185.5"
median, 1991–2020
median, 1991–2020
28 of 28 observed
NOAA normal
Frost risk by date in Bessemer
Half of springs at Ironwood #2, MI see their last 32°F night by May 19; only one in ten is past it by May 2, and one in ten still has one after June 3. Planting tender crops after May 26 leaves a 30% risk of a frost on them, after May 30 20%, and after June 3 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 September 28 in half of years, as early as September 12 one year in ten, and holds off past October 10 one year in ten. A hard freeze of 28°F follows 11 days later, around October 9; in spring the one-in-ten date for 28°F is May 21, 13 days before the 32°F one. The freeze-free season lasts 130 days in a typical year, shorter than at 85% of the 172 Michigan stations; it reaches 152 days one year in ten and falls short of 108 one year in ten. On average 203 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 31, and return around September 17. Severe cold of 16°F or below comes every winter, usually between November 13 and April 9.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 18 | May 22 | May 26 | May 29 | May 31 | Jun 3 | Jun 6 | Jun 10 | Jun 17 |
| 32°F | May 2 | May 7 | May 11 | May 15 | May 19 | May 22 | May 26 | May 30 | Jun 3 |
| 28°F | Apr 23 | Apr 27 | Apr 30 | May 2 | May 5 | May 8 | May 11 | May 16 | May 21 |
| 24°F | Apr 13 | Apr 18 | Apr 21 | Apr 23 | Apr 26 | Apr 28 | Apr 30 | May 3 | May 9 |
| 20°F | Apr 4 | Apr 8 | Apr 12 | Apr 14 | Apr 17 | Apr 20 | Apr 22 | Apr 25 | Apr 28 |
| 16°F | Mar 28 | Apr 1 | Apr 4 | Apr 6 | Apr 9 | Apr 12 | Apr 15 | Apr 18 | Apr 21 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 1 | Sep 4 | Sep 9 | Sep 13 | Sep 17 | Sep 19 | Sep 22 | Sep 26 | Sep 30 |
| 32°F | Sep 12 | Sep 18 | Sep 22 | Sep 25 | Sep 28 | Oct 1 | Oct 3 | Oct 6 | Oct 10 |
| 28°F | Sep 23 | Sep 29 | Oct 3 | Oct 6 | Oct 9 | Oct 12 | Oct 15 | Oct 20 | Oct 24 |
| 24°F | Oct 7 | Oct 12 | Oct 16 | Oct 20 | Oct 24 | Oct 27 | Oct 30 | Nov 2 | Nov 6 |
| 20°F | Oct 22 | Oct 27 | Oct 31 | Nov 1 | Nov 4 | Nov 6 | Nov 10 | Nov 13 | Nov 18 |
| 16°F | Nov 1 | Nov 3 | Nov 7 | Nov 10 | Nov 13 | Nov 15 | Nov 18 | Nov 22 | Nov 26 |
Freeze probabilities 1991–2020 at Ironwood #2, 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 49911 →Compare Bessemer with another place →
Compared with the next station
The nearest other station, Hurley, WI, 7 miles west of Bessemer, has a last frost 5 days later (May 24), the same first-frost date, a season 2 days shorter.
When it snows in Bessemer, Michigan
The first measurable snow (0.1 inch or more) in Bessemer usually arrives around October 19, and the last of the season around April 29. Those are the middle dates across the winters of 1991–2020 at Ironwood, MI, 6.6 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 20 days after the last snow.
Planting calendar for 49911
| When | What to do |
|---|---|
| March 10 – March 24 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 24 – April 7 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 21 – May 5 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 19 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 6 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 14 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| September 28 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 49911 is 4 miles from Ironwood #2, MI, which stands at 1,520 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 49938 (Ironwood). The 2023 USDA Plant Hardiness Zone Map lists ZIP 49911 in zone 4b, the band where the coldest night of the year averaged -25 to -20°F (-31.7 to -28.9°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.