USDA Hardiness Zone 6b
Frost Dates for 48161 — Monroe, Michigan
NOAA 1991–2020 normals from Monroe, MI (586 ft), under a mile north.
Updated
In Monroe, the last spring frost (32°F) is around April 23 in half of years and has passed by May 7 in nine years out of ten. The first fall frost comes around October 23, as early as October 9 one year in ten, leaving a typical freeze-free season of 182 days (NOAA, Monroe, MI).
- Last spring frost
- April 23
- First fall frost
- October 23
- Growing season
- 182 days
- Hardiness zone
- 6b
50% probability
50% probability
freeze-free, 50%
-5 to 0°F (-20.6 to -17.8°C) coldest night
- First snow
- December 1
- Last snow
- March 30
- Winters with snow
- 100%
- Snow per year
- 41.2"
median, 1991–2020
median, 1991–2020
16 of 16 observed
NOAA normal
Frost risk by date in Monroe
Half of springs at Monroe, MI see their last 32°F night by April 23; only one in ten is past it by April 8, and one in ten still has one after May 7. Planting tender crops after April 29 leaves a 30% risk of a frost on them, after May 2 20%, and after May 7 10%. The 14 days between the even-odds date and the one-in-ten date is narrower than at 80% of the 172 Michigan stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 23 in half of years, as early as October 9 one year in ten, and holds off past November 5 one year in ten. A hard freeze of 28°F follows 12 days later, around November 4; in spring the one-in-ten date for 28°F is April 27, 10 days before the 32°F one. The freeze-free season lasts 182 days in a typical year, longer than at 97% of the 172 Michigan stations; it reaches 202 days one year in ten and falls short of 162 one year in ten. On average 128 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 9 days longer, to about May 2, and return around October 11. Severe cold of 16°F or below comes every winter, usually between December 6 and March 15.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 20 | Apr 25 | Apr 28 | Apr 30 | May 2 | May 5 | May 8 | May 11 | May 16 |
| 32°F | Apr 8 | Apr 14 | Apr 17 | Apr 20 | Apr 23 | Apr 25 | Apr 29 | May 2 | May 7 |
| 28°F | Mar 31 | Apr 4 | Apr 7 | Apr 10 | Apr 14 | Apr 16 | Apr 18 | Apr 22 | Apr 27 |
| 24°F | Mar 18 | Mar 24 | Mar 29 | Apr 1 | Apr 2 | Apr 5 | Apr 8 | Apr 11 | Apr 17 |
| 20°F | Mar 9 | Mar 14 | Mar 17 | Mar 21 | Mar 24 | Mar 27 | Mar 30 | Apr 1 | Apr 6 |
| 16°F | Feb 27 | Mar 5 | Mar 9 | Mar 12 | Mar 15 | Mar 18 | Mar 22 | Mar 26 | Mar 30 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 28 | Oct 2 | Oct 6 | Oct 9 | Oct 11 | Oct 14 | Oct 17 | Oct 20 | Oct 26 |
| 32°F | Oct 9 | Oct 14 | Oct 18 | Oct 21 | Oct 23 | Oct 25 | Oct 29 | Nov 1 | Nov 5 |
| 28°F | Oct 21 | Oct 26 | Oct 30 | Nov 1 | Nov 4 | Nov 6 | Nov 9 | Nov 13 | Nov 18 |
| 24°F | Nov 2 | Nov 7 | Nov 10 | Nov 12 | Nov 15 | Nov 18 | Nov 21 | Nov 25 | Dec 1 |
| 20°F | Nov 11 | Nov 16 | Nov 19 | Nov 23 | Nov 26 | Nov 30 | Dec 3 | Dec 7 | Dec 13 |
| 16°F | Nov 19 | Nov 25 | Nov 30 | Dec 3 | Dec 6 | Dec 10 | Dec 14 | Dec 18 | Dec 23 |
Freeze probabilities 1991–2020 at Monroe, 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 48161 →Compare Monroe with another place →
Weather by month in Monroe
July is the warmest month at Monroe, MI, averaging 85°F by day and 63°F at night; January is the coldest at 33°F and 18°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 24% of years.
Warmth for growing adds up to 2,979 growing degree days a year (base 50°F), more than at 95% of the 172 Michigan stations. 33% of them (988) have built up by the end of June, and July adds the most, 728.
| Month | High °F | Low °F | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|
| Jan | 33 | 18 | 100% | 28 | 1 |
| Feb | 35 | 19 | 100% | 26 | 1 |
| Mar | 45 | 27 | 100% | 22 | 18 |
| Apr | 58 | 38 | 98% | 7 | 79 |
| May | 69 | 49 | 24% | 1 | 303 |
| Jun | 80 | 59 | 0% | 0 | 588 |
| Jul | 85 | 63 | 0% | 0 | 728 |
| Aug | 82 | 61 | 0% | 0 | 659 |
| Sep | 75 | 54 | 1% | 0 | 434 |
| Oct | 63 | 42 | 76% | 3 | 147 |
| Nov | 49 | 33 | 100% | 16 | 21 |
| Dec | 38 | 24 | 100% | 26 | 2 |
Monthly normals 1991–2020 at Monroe, MI (586 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, Newport 4SSE, MI, 8 miles northeast of Monroe, has a last frost 4 days later (April 27), a first frost 1 day earlier (October 22), a season 5 days shorter.
When it snows in Monroe, Michigan
The first measurable snow (0.1 inch or more) in Monroe usually arrives around December 1, and the last of the season around March 30. Those are the middle dates across the winters of 1991–2020 at Newport 4SSE, MI, 7.7 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 24 days after the last snow.
Planting calendar for 48161
| When | What to do |
|---|---|
| February 12 – February 26 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 26 – March 12 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 26 – April 9 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 23 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 31 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 9 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 23 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 48161 is under a mile from Monroe, MI, which stands at 586 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 5 other ZIP codes share the station; its figures are presented in full for 48162 (Monroe). The 2023 USDA Plant Hardiness Zone Map lists ZIP 48161 in zone 6b, the band where the coldest night of the year averaged -5 to 0°F (-20.6 to -17.8°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.