USDA Hardiness Zone 6a
Frost Dates for 53172 — South Milwaukee, Wisconsin
NOAA 1991–2020 normals from South Milwaukee Wwtp, WI (650 ft), 1 miles southeast.
Updated
In South Milwaukee, the last spring frost (32°F) is around April 22 in half of years and has passed by May 8 in nine years out of ten. The first fall frost comes around October 26, as early as October 10 one year in ten, leaving a typical freeze-free season of 184 days (NOAA, South Milwaukee Wwtp, WI).
- Last spring frost
- April 22
- First fall frost
- October 26
- Growing season
- 184 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 13
- Last snow
- April 13
- Winters with snow
- 100%
- Snow per year
- 48.7"
median, 1991–2020
median, 1991–2020
30 of 30 observed
NOAA normal
Frost risk by date in South Milwaukee
Half of springs at South Milwaukee Wwtp, WI see their last 32°F night by April 22; only one in ten is past it by April 9, and one in ten still has one after May 8. Planting tender crops after April 29 leaves a 30% risk of a frost on them, after May 1 20%, and after May 8 10%. The 16 days between the even-odds date and the one-in-ten date is wider than at 70% of the 182 Wisconsin 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 10 one year in ten, and holds off past November 8 one year in ten. A hard freeze of 28°F follows 10 days later, around November 5; in spring the one-in-ten date for 28°F is April 24, 14 days before the 32°F one. The freeze-free season lasts 184 days in a typical year, longer than at 98% of the 182 Wisconsin stations; it reaches 203 days one year in ten and falls short of 163 one year in ten. On average 124 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 13 days longer, to about May 5, and return around October 16. Severe cold of 16°F or below comes every winter, usually between December 3 and March 10.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 21 | Apr 26 | Apr 30 | May 2 | May 5 | May 8 | May 12 | May 18 | May 24 |
| 32°F | Apr 9 | Apr 13 | Apr 16 | Apr 19 | Apr 22 | Apr 25 | Apr 29 | May 1 | May 8 |
| 28°F | Mar 28 | Apr 2 | Apr 5 | Apr 7 | Apr 9 | Apr 13 | Apr 16 | Apr 19 | Apr 24 |
| 24°F | Mar 15 | Mar 21 | Mar 25 | Mar 28 | Mar 31 | Apr 2 | Apr 5 | Apr 8 | Apr 13 |
| 20°F | Mar 6 | Mar 10 | Mar 14 | Mar 16 | Mar 19 | Mar 22 | Mar 26 | Mar 29 | Apr 2 |
| 16°F | Feb 25 | Mar 2 | Mar 5 | Mar 8 | Mar 10 | Mar 13 | Mar 16 | Mar 20 | Mar 25 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 1 | Oct 7 | Oct 10 | Oct 14 | Oct 16 | Oct 19 | Oct 22 | Oct 25 | Oct 28 |
| 32°F | Oct 10 | Oct 16 | Oct 20 | Oct 24 | Oct 26 | Oct 28 | Oct 31 | Nov 3 | Nov 8 |
| 28°F | Oct 24 | Oct 30 | Nov 1 | Nov 3 | Nov 5 | Nov 8 | Nov 11 | Nov 15 | Nov 20 |
| 24°F | Nov 3 | Nov 6 | Nov 9 | Nov 12 | Nov 15 | Nov 18 | Nov 22 | Nov 26 | Dec 1 |
| 20°F | Nov 9 | Nov 13 | Nov 18 | Nov 21 | Nov 24 | Nov 27 | Dec 1 | Dec 4 | Dec 11 |
| 16°F | Nov 17 | Nov 23 | Nov 27 | Dec 1 | Dec 3 | Dec 6 | Dec 10 | Dec 15 | Dec 21 |
Freeze probabilities 1991–2020 at South Milwaukee 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 53172 →Compare South Milwaukee with another place →
Weather by month in South Milwaukee
July is the warmest month at South Milwaukee Wwtp, WI, averaging 80°F by day and 65°F at night; January is the coldest at 30°F and 16°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 23% of years.
Warmth for growing adds up to 2,716 growing degree days a year (base 50°F), more than at 85% of the 182 Wisconsin stations. 27% of them (740) have built up by the end of June, and July adds the most, 699. Precipitation totals 36.6 inches a year, most in June (4.6") and least in January (1.7"); May to September bring 53% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 30 | 16 | 1.7 | 100% | 29 | 0 |
| Feb | 33 | 18 | 1.8 | 100% | 26 | 1 |
| Mar | 42 | 28 | 2.2 | 100% | 21 | 10 |
| Apr | 53 | 37 | 4.1 | 99% | 7 | 42 |
| May | 64 | 47 | 4.2 | 23% | <1 | 210 |
| Jun | 75 | 57 | 4.6 | 0% | 0 | 478 |
| Jul | 80 | 65 | 3.5 | 0% | 0 | 699 |
| Aug | 79 | 64 | 3.8 | 0% | 0 | 674 |
| Sep | 73 | 56 | 3.3 | 1% | 0 | 436 |
| Oct | 61 | 44 | 3.4 | 71% | 3 | 143 |
| Nov | 48 | 33 | 2.1 | 100% | 14 | 22 |
| Dec | 36 | 22 | 1.9 | 100% | 25 | 1 |
Monthly normals 1991–2020 at South Milwaukee Wwtp, WI (650 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, Milwaukee Mitchell Airport, WI, 4 miles northwest of South Milwaukee, has a last frost 3 days earlier (April 19), a first frost 3 days later (October 29), a season 8 days longer.
When it snows in South Milwaukee, Wisconsin
The first measurable snow (0.1 inch or more) in South Milwaukee usually arrives around November 13, and the last of the season around April 13. Those are the middle dates across the winters of 1991–2020 at Milwaukee Mitchell Airport, WI, 3.7 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 9 days after the last snow.
Planting calendar for 53172
| When | What to do |
|---|---|
| February 11 – February 25 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 25 – March 11 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 25 – April 8 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 22 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 53172 is 1 mile from South Milwaukee Wwtp, WI, which stands at 650 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 53154 (Oak Creek). The 2023 USDA Plant Hardiness Zone Map lists ZIP 53172 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.
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.