Milwaukee, Wisconsin: planting zone & frost dates
Milwaukee is in USDA plant hardiness zone 6a, where the average coldest winter night reaches -10 to -5°F (-23.3 to -20.6°C). The typical last spring frost is around May 2 and the first fall frost around Oct 12.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | May 12 | Oct 2 |
| Typical planning date (30% risk) | May 2 | Oct 12 |
| Median (50%) | Apr 26 | Oct 18 |
How to read this: after the spring "10% risk" date, a 32°F frost happens in only about 1 year in 10. In fall, the "10% risk" date is the early end — a frost before it happens about 1 year in 10.
Frost data comes from NOAA station MT MARY COLLEGE, WI (USC00475474), 3.2 mi (5.2 km) from the city center and 7 ft higher than the city center (+2 m). Record used for the 1991–2020 normals: 28 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Milwaukee
Milwaukee spans more than one half-zone. Share of the city's land area by zone (via its 24 ZIP codes): 6a (74%), 5b (26%). The headline zone is the one covering the most land. Look up your ZIP for your exact zone.
ZIP codes in Milwaukee and their zones
Vegetable planting calendar for Milwaukee
Dates are counted from the 30%-risk frost dates above (last frost May 2, first frost Oct 12). Shift a week later in cold spots or low-lying ground.
| Crop | Start indoors | Transplant / plant out | Direct sow | Fall crop sow/plant |
|---|---|---|---|---|
| Tomato | Mar 7 – Mar 21 | May 9 – May 23 | — | — |
| Pepper | Feb 21 – Mar 7 | May 16 – May 30 | — | — |
| Lettuce | Mar 21 – Apr 4 | Apr 18 – May 9 | Apr 4 – May 16 | Aug 3 – Aug 31 |
| Green Beans | — | — | May 9 – Jun 13 | Jul 20 – Aug 3 |
| Sweet Corn | — | — | May 9 – Jun 6 | — |
| Zucchini & Summer Squash | Apr 4 – Apr 11 | May 9 – May 23 | May 9 – May 30 | Jul 20 – Aug 3 |
| Cucumber | Apr 4 – Apr 11 | May 16 – May 23 | May 9 – May 30 | Jul 20 – Aug 3 |
| Carrot | — | — | Apr 11 – May 16 | Jul 20 – Aug 3 |
| Onion | Feb 7 – Feb 21 | Apr 4 – Apr 18 | — | — |
| Potato | — | Apr 4 – Apr 25 | — | — |
| Basil | Mar 21 – Apr 4 | May 16 – May 30 | May 16 – Jun 6 | — |
| Spinach | — | — | Mar 21 – Apr 18 | Aug 17 – Sep 14 |
| Kale | Mar 7 – Mar 21 | Apr 4 – Apr 25 | Apr 4 – Apr 25 | Aug 3 – Aug 31 |
| Broccoli | Mar 7 – Mar 21 | Apr 18 – May 9 | — | Jul 20 – Aug 3 |
| Peas | — | — | Mar 21 – Apr 11 | Aug 3 – Aug 17 |
| Eggplant | Feb 21 – Mar 7 | May 16 – May 30 | — | — |
| Cabbage | Mar 7 – Mar 21 | Apr 4 – Apr 18 | — | Jul 20 – Aug 3 |
| Radish | — | — | Mar 28 – May 16 | Aug 31 – Sep 28 |
| Strawberry | — | Apr 4 – Apr 25 | — | — |
| Beets | — | — | Apr 11 – May 23 | Aug 3 – Aug 17 |
Nearby cities in Wisconsin
- Racine — zone 6a, last frost Apr 27, first frost Oct 18
- Kenosha — zone 5b, last frost May 3, first frost Oct 14
- Green Bay — zone 5b, last frost May 13, first frost Oct 2
- Madison — zone 5b, last frost May 7, first frost Oct 3
More: all Wisconsin cities · other zone 6a cities: Chicago, IL, Denver, CO, Colorado Springs, CO, Omaha, NE, Aurora, CO, Lincoln, NE, Fort Wayne, IN, Worcester, MA
Milwaukee gardening questions
When is the last frost in Milwaukee, WI?
Plan around May 2. At NOAA's Mt Mary College, WI station, 3.2 mi from the city center, there is a 30% chance of a 32°F frost after that date. Half of springs have their last frost by Apr 26, and after May 12 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Apr 14. The 90% and 10% dates are 30 days apart, close to the 36-day median for cities on this site.
When should I plant tomatoes in Milwaukee, WI?
Start seeds indoors Mar 7 – Mar 21 and set transplants outside May 9 – May 23, once nights stay above 50°F and the soil is near 60°F. That leaves 163 days between the 30% frost dates, enough for most varieties including 80–85-day slicers. More: tomato planting dates by zone.
How long is the growing season in Milwaukee?
About 173 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 153 days, and in 1 year in 10 it runs 192 days or more. In fall there is a 10% chance of frost by Oct 2 and a 30% chance by Oct 12. That ranks 3rd longest of 5 Wisconsin cities on this site.
When should I plant a fall garden in Milwaukee?
Count back from the first fall frost (Oct 12): transplant broccoli Jul 20 – Aug 3; sow kale Aug 3 – Aug 31; sow lettuce Aug 3 – Aug 31; sow radishes Aug 31 – Sep 28. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Oct 30. How the math works: succession and fall planting.
Did Milwaukee's hardiness zone change on the 2023 map?
Yes. Most of Milwaukee was zone 5b on the 2012 map and is zone 6a on the 2023 map — half a zone warmer, like about 56% of U.S. ZIP codes. The shift comes from a newer 1991–2020 averaging period plus more weather stations and better mapping; it does not mean last frost comes earlier. Why the 2023 map is warmer.
Is all of Milwaukee in zone 6a?
No. Zone 6a covers about 74% of the city's land; the rest is in 5b (26%), measured across the city's 24 ZIP codes. Check your own ZIP code in the table above or with the ZIP lookup.