USDA Hardiness Zone 5b
Frost Dates for 53551 — Lake Mills, Wisconsin
NOAA 1991–2020 normals from Lake Mills Wwtp, WI (811 ft), under a mile east.
Updated
In Lake Mills, the last spring frost (32°F) is around April 29 in half of years and has passed by May 13 in nine years out of ten. The first fall frost comes around October 14, as early as September 29 one year in ten, leaving a typical freeze-free season of 167 days (NOAA, Lake Mills Wwtp, WI).
- Last spring frost
- April 29
- First fall frost
- October 14
- Growing season
- 167 days
- Hardiness zone
- 5b
50% probability
50% probability
freeze-free, 50%
-15 to -10°F (-26.1 to -23.3°C) coldest night
- First snow
- November 23
- Last snow
- March 28
- Winters with snow
- 100%
- Snow per year
- 42.3"
median, 1991–2020
median, 1991–2020
30 of 30 observed
NOAA normal
Frost risk by date in Lake Mills
Half of springs at Lake Mills Wwtp, WI see their last 32°F night by April 29; only one in ten is past it by April 15, and one in ten still has one after May 13. Planting tender crops after May 4 leaves a 30% risk of a frost on them, after May 7 20%, and after May 13 10%. The 14 days between the even-odds date and the one-in-ten date is narrower than at 58% of the 182 Wisconsin stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 14 in half of years, as early as September 29 one year in ten, and holds off past October 27 one year in ten. A hard freeze of 28°F follows 12 days later, around October 26; in spring the one-in-ten date for 28°F is May 3, 10 days before the 32°F one. The freeze-free season lasts 167 days in a typical year, longer than at 79% of the 182 Wisconsin stations; it reaches 186 days one year in ten and falls short of 146 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 9 days longer, to about May 8, and return around October 3. Severe cold of 16°F or below comes every winter, usually between November 24 and March 18.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 26 | Apr 30 | May 3 | May 5 | May 8 | May 11 | May 14 | May 17 | May 22 |
| 32°F | Apr 15 | Apr 20 | Apr 23 | Apr 27 | Apr 29 | May 1 | May 4 | May 7 | May 13 |
| 28°F | Apr 4 | Apr 7 | Apr 11 | Apr 14 | Apr 17 | Apr 20 | Apr 24 | Apr 29 | May 3 |
| 24°F | Mar 23 | Mar 29 | Apr 1 | Apr 3 | Apr 5 | Apr 8 | Apr 11 | Apr 14 | Apr 21 |
| 20°F | Mar 12 | Mar 17 | Mar 21 | Mar 24 | Mar 27 | Mar 30 | Apr 1 | Apr 4 | Apr 9 |
| 16°F | Mar 4 | Mar 9 | Mar 12 | Mar 15 | Mar 18 | Mar 21 | Mar 23 | Mar 27 | Mar 31 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 20 | Sep 25 | Sep 28 | Oct 1 | Oct 3 | Oct 5 | Oct 8 | Oct 12 | Oct 16 |
| 32°F | Sep 29 | Oct 4 | Oct 8 | Oct 11 | Oct 14 | Oct 17 | Oct 20 | Oct 23 | Oct 27 |
| 28°F | Oct 8 | Oct 16 | Oct 21 | Oct 24 | Oct 26 | Oct 29 | Oct 31 | Nov 3 | Nov 8 |
| 24°F | Oct 25 | Oct 30 | Nov 1 | Nov 4 | Nov 6 | Nov 9 | Nov 13 | Nov 17 | Nov 21 |
| 20°F | Nov 2 | Nov 6 | Nov 10 | Nov 14 | Nov 17 | Nov 20 | Nov 22 | Nov 25 | Nov 30 |
| 16°F | Nov 8 | Nov 14 | Nov 19 | Nov 21 | Nov 24 | Nov 27 | Nov 30 | Dec 3 | Dec 11 |
Freeze probabilities 1991–2020 at Lake Mills Wwtp, WI, 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 53551 →Compare Lake Mills with another place →
Weather by month in Lake Mills
July is the warmest month at Lake Mills Wwtp, WI, averaging 84°F by day and 62°F at night; January is the coldest at 27°F and 11°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 44% of years.
Warmth for growing adds up to 2,830 growing degree days a year (base 50°F), more than at 93% of the 182 Wisconsin stations. 33% of them (947) have built up by the end of June, and July adds the most, 711. Precipitation totals 37.0 inches a year, most in June (5.1") and least in January (1.4"); May to September bring 59% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 27 | 11 | 1.4 | 100% | 30 | 0 |
| Feb | 31 | 14 | 1.5 | 100% | 27 | 1 |
| Mar | 43 | 25 | 2.0 | 100% | 24 | 14 |
| Apr | 57 | 36 | 3.6 | 100% | 10 | 68 |
| May | 70 | 48 | 4.4 | 44% | 1 | 292 |
| Jun | 80 | 58 | 5.1 | 0% | 0 | 573 |
| Jul | 84 | 62 | 4.4 | 0% | 0 | 711 |
| Aug | 81 | 61 | 4.5 | 0% | 0 | 645 |
| Sep | 74 | 52 | 3.5 | 12% | <1 | 392 |
| Oct | 61 | 40 | 2.8 | 93% | 6 | 122 |
| Nov | 45 | 29 | 2.1 | 100% | 19 | 13 |
| Dec | 32 | 18 | 1.7 | 100% | 29 | 1 |
Monthly normals 1991–2020 at Lake Mills Wwtp, WI (811 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, Jefferson Wwtp, WI, 8 miles southeast of Lake Mills, has a last frost 4 days earlier (April 25), a first frost 4 days later (October 18), a season 6 days longer.
When it snows in Lake Mills, Wisconsin
The first measurable snow (0.1 inch or more) in Lake Mills usually arrives around November 23, and the last of the season around March 28. Those are the middle dates across the winters of 1991–2020 at Lake Mills Wwtp, WI, 0.6 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 32 days after the last snow.
Planting calendar for 53551
| When | What to do |
|---|---|
| February 18 – March 4 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 4 – March 18 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 1 – April 15 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 29 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 22 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 30 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 14 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 53551 is under a mile from Lake Mills Wwtp, WI, which stands at 811 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 53551 in zone 5b, the band where the coldest night of the year averaged -15 to -10°F (-26.1 to -23.3°C) over 1991–2020; a zone describes winter lows, not frost dates.
Frost dates across Wisconsin →
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.