Wisconsin weather and outdoor projects
Wisconsin has cold winters and warm summers, with Lake Michigan cooling springs near the shore. Milwaukee is a little milder than Green Bay and the north, where frost comes early in fall and the outdoor season is shorter.
June through early September is the best window for staining, painting and concrete. Spring can be cool and wet, especially near the lake. Hard freezes begin in October, and long winters with freeze-thaw cycles and road salt are hard on concrete, so curing and sealing new flatwork matters.
Frost dates in Wisconsin
In Milwaukee, the median last spring freeze (32°F) is around April 19 and the median first fall freeze is around October 29, a frost-free season of about 192 days.
In Green Bay, the median last spring freeze (32°F) is around April 30 and the median first fall freeze is around October 9, a frost-free season of about 161 days.
How Wisconsin compares with other states
Milwaukee is tied for the 5th-most humid summer afternoons of the 47 state main stations (58% humidity at 3 PM, June–August). Milwaukee has the 6th-fewest days at 90°F or hotter of the 50 state main stations (9 a year). Milwaukee is tied for the 14th-shortest deck staining season of the 50 state main stations (4 good months).
| Measure (Milwaukee) | Value | Rank, highest first |
|---|---|---|
| Deck staining season | 4 good months | 20th of 50 |
| Frost-free season | 192 days | 33rd of 50 |
| Freezing nights | 123 a year | 14th of 50 |
| Rainy days | 69 a year with 0.1 in or more | 31st of 50 |
| Days at 90°F or hotter | 9 a year | 45th of 50 |
| Summer afternoons | 58% humidity at 3 PM, June–August | 5th of 47 |
Best time to stain a deck in Wisconsin
In Milwaukee, the most reliable months are June–September. May and October can also work on the right days (average highs May 67°F, Oct 61°F). November–April is too cold, with average highs around 41°F. In May, nights average about 48°F, so finish early on mild days and check the overnight low. October is cool, with highs around 61°F, so choose the warmest afternoons.
In Green Bay, the most reliable months are June–September. May and October can also work on the right days (average highs May 67°F, Oct 58°F). November–April is too cold, with average highs around 37°F. In May, nights average about 46°F, so finish early on mild days and check the overnight low. October is cool, with highs around 58°F, so choose the warmest afternoons.
Best time to paint outside in Wisconsin
In Milwaukee, the most reliable months are May–September. April and October can also work on the right days (average highs Apr 55°F, Oct 61°F). November–March is too cold, with average highs around 39°F. April is cool, with highs around 55°F, so choose the warmest afternoons. In October, nights average about 45°F, so finish early on mild days and check the overnight low.
In Green Bay, the most reliable months are May–September. April and October can also work on the right days (average highs Apr 54°F, Oct 58°F). November–March is too cold, with average highs around 34°F. April is cool, with highs around 54°F, so choose the warmest afternoons. In October, nights average about 40°F, so finish early on mild days and check the overnight low.
Best time to pour concrete in Wisconsin
In Milwaukee, the most reliable months are May–September. April and October can also work on the right days (average highs Apr 55°F, Oct 61°F). November–March averages about 23 nights a month at or below 32°F, so fresh concrete needs blankets or heated enclosures. April and October bring about 4 freezing nights a month, so pick a mild spell and keep curing blankets on hand.
In Green Bay, the most reliable months are May–September. October can also work on the right days (average highs Oct 58°F). November–April averages about 24 nights a month at or below 32°F, so fresh concrete needs blankets or heated enclosures. October brings about 8 freezing nights a month, so pick a mild spell and keep curing blankets on hand.
Best time to seal a driveway in Wisconsin
In Milwaukee, the most reliable months are June–September. May and October can also work on the right days (average highs May 67°F, Oct 61°F). November–April is too cold, with average highs around 41°F. May and October are cool, with highs around 64°F, so choose the warmest afternoons.
In Green Bay, the most reliable months are June–August. May and September can also work on the right days (average highs May 67°F, Sep 72°F). October–April is too cold, with average highs around 40°F. May is cool, with highs around 67°F, so choose the warmest afternoons. In September, nights average about 50°F, so finish early on mild days and check the overnight low.
Best time to fertilize or treat a lawn in Wisconsin
In Milwaukee, the most reliable months are May–October. April can also work on the right days (average highs Apr 55°F). November–March is too cold, with average highs around 39°F. April is cool, with highs around 55°F, so choose the warmest afternoons.
In Green Bay, the most reliable months are May–September. April and October can also work on the right days (average highs Apr 54°F, Oct 58°F). November–March is too cold, with average highs around 34°F. April and October are cool, with highs around 56°F, so choose the warmest afternoons.
How the weather differs across Wisconsin
| Place | Hottest month avg high | Coldest month avg low | Rain per year | Last spring freeze | First fall freeze |
|---|---|---|---|---|---|
| Milwaukee | 82°F | 17°F | 35 in | April 19 | October 29 |
| Green Bay | 81°F | 11°F | 32 in | April 30 | October 9 |
Monthly weather in Milwaukee
| Month | Avg high | Avg low | Wet days* | Rain | 3 PM humidity | Freezing nights |
|---|---|---|---|---|---|---|
| January | 31°F | 17°F | 5 | 1.8 in | 64% | 28 |
| February | 34°F | 20°F | 4 | 1.7 in | 61% | 25 |
| March | 44°F | 29°F | 5 | 2.2 in | 56% | 21 |
| April | 55°F | 38°F | 7 | 3.9 in | 53% | 6 |
| May | 67°F | 48°F | 7 | 3.5 in | 55% | 0 |
| June | 77°F | 58°F | 7 | 4.4 in | 57% | 0 |
| July | 82°F | 65°F | 6 | 3.4 in | 57% | 0 |
| August | 80°F | 64°F | 6 | 3.6 in | 59% | 0 |
| September | 74°F | 56°F | 5 | 3.2 in | 58% | 0 |
| October | 61°F | 45°F | 6 | 2.8 in | 56% | 2 |
| November | 48°F | 33°F | 5 | 2.2 in | 59% | 15 |
| December | 36°F | 23°F | 5 | 1.9 in | 65% | 25 |
*Days with 0.1 inch of rain or more; column notes.
Monthly weather in Green Bay
| Month | Avg high | Avg low | Wet days* | Rain | 3 PM humidity | Freezing nights |
|---|---|---|---|---|---|---|
| January | 26°F | 11°F | 4 | 1.4 in | 67% | 30 |
| February | 29°F | 13°F | 4 | 1.2 in | 62% | 27 |
| March | 40°F | 24°F | 5 | 2.0 in | 57% | 25 |
| April | 54°F | 35°F | 7 | 3.0 in | 50% | 12 |
| May | 67°F | 46°F | 7 | 3.4 in | 50% | 1 |
| June | 77°F | 56°F | 8 | 4.1 in | 55% | 0 |
| July | 81°F | 60°F | 7 | 3.6 in | 55% | 0 |
| August | 79°F | 58°F | 6 | 3.4 in | 57% | 0 |
| September | 72°F | 50°F | 6 | 3.2 in | 56% | 1 |
| October | 58°F | 40°F | 6 | 2.7 in | 56% | 8 |
| November | 44°F | 29°F | 5 | 2.0 in | 61% | 21 |
| December | 31°F | 18°F | 5 | 1.8 in | 69% | 28 |
Source: NOAA NCEI U.S. Climate Normals 1991–2020 for MILWAUKEE MITCHELL AP, GREEN BAY. See how the ratings work and how late in fall you can stain, paint or seal.
Frequently asked questions
When is the best time to stain a deck in Wisconsin?
In Milwaukee, June–September. In Green Bay, June–September.
When is the last frost in Wisconsin?
Milwaukee: around April 19; Green Bay: around April 30.
Can you pour concrete in winter in Wisconsin?
Yes, with cold-weather practices: Milwaukee averages about 79 freezing nights from December to February, so fresh concrete needs insulated blankets, a heated enclosure or an accelerated mix, and must not freeze in the first 48 hours. Many homeowners wait for spring.
What months are best for sealing a driveway in Wisconsin?
In Milwaukee, June–September. In Green Bay, June–August.