Milwaukee, Wisconsin Frost Dates, Growing Season & Hardiness Zone

When is the last frost in Milwaukee?

The typical last 32°F night is Apr 26, and in 1 year out of 10 a freeze still comes after May 12. Cold 36°F nights (frost possible on plants) typically last longer, to around May 8. The last hard freeze (28°F) typically comes earlier, around Apr 14.

In Milwaukee, late frosts can come well after the typical date. The safer 1-in-10 date (May 12) is 16 days after the typical date (Apr 26). Tender plants set out early will need cover on cold nights.

Cold nights don't end with the last freeze. The typical last 36°F night (frost possible on plants in low spots) comes around May 8, 12 days after the typical last 32°F night. On clear, calm nights, frost can form on leaves while the thermometer still reads above freezing.

Is it too early to plant in Milwaukee?

Before Apr 26 the odds of another 32°F night are better than even; after May 12 they are about 1 in 10 or less.

Today's risk is computed in your browser from the same NOAA probability table, shown as the range between the two nearest NOAA probability levels.

When is the first frost in Milwaukee?

By Oct 18, half of years have had their first 32°F night. In 1 year out of 10, it comes as early as Oct 2. In a typical year, look for the first 36°F night (frost possible on plants) around Oct 6 and the first 28°F hard freeze around Oct 30.

Fall plantings are timed backward from first frost: Oct 18 typically, or Oct 2 if you want a cushion. See the planting calendar for each crop's date.

How long is Milwaukee's growing season?

Milwaukee's frost-free season (32°F) typically runs 173 days. In about 1 year out of 10, it's shorter than 153 days.

A season this long fits most warm-season vegetables planted on time. Long-season crops do best when started from transplants.

Growing degree days measure the heat available for crops to grow. The station averages 2,804 a year (base 50°F).

How does Milwaukee's season compare?

Nationwide, across the 56 cities with frost dates on this site, the typical frost-free season here outlasts the one in 20 of them and falls short of the one in 35.

Growing degree days (base 50°F)

Annual normal: 2,804 GDD (NOAA flag S, 25 years). Running total by the end of each month (sum of NOAA daily GDD normals, so the year-end total can differ slightly from the annual normal):

What growing zone is Milwaukee? (USDA 2023)

The 2023 USDA map puts Milwaukee in zone 5b–6a (-15 to -5°F average coldest winter night). On the 2012 map, most of the city was 5b. Comparing ZIPs listed in both tables, 20 of 30 moved up half a zone.

Zones: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed 2026-10-08. Shown as published in the ZIP tables; this page does not show a zone map. Not the official USDA Plant Hardiness Zone Map (official map: planthardiness.ars.usda.gov).

Does the new zone change Milwaukee's frost dates?

No. Hardiness zones are based only on the average coldest winter temperature. They say nothing about when spring and fall frosts happen. Milwaukee's frost dates come from NOAA's 1991–2020 frost probabilities, which did not change with the 2023 zone map. Use your zone to pick perennials that will survive winter, and your frost dates to time planting.

Why do Milwaukee frost dates differ between websites?

You may see May 2 given as Milwaukee's last frost date. That's the 30%-risk date, meaning about 3 years in 10 still have a 32°F night after it. Our headline date is Apr 26, the 50% (median) date.

May 12 is the 10%-risk, or 'safer', date. Only about 1 year in 10 has a 32°F night after it.

You may also see May 8. That's the 50% date for a 36°F night (frost possible on plants) rather than a 32°F freeze, so sites using 36°F as their cutoff list later dates.

Sites also pick different weather stations. Within 25 miles of the city center, the 14 stations that meet our quality rules put the typical (50%) last 32°F frost anywhere from Apr 19 to May 6 (table below).

Which weather station is this based on?

Station

Mount Mary College (NOAA USC00475474, COOP)

Distance

3.2 mi W of the city center

Elevation

715 ft; city center 710 ft (USGS), difference +5 ft

Record

NOAA completeness flag S, 28 of 30 years (1991–2020)

Confidence

High (rule)

Confidence: High. At 3.2 miles from the city center and only 5 ft off in elevation, with frost statistics that meet our completeness rule (NOAA flag S, 28 of 30 years), this station is a close match.

Milwaukee planting dates at a glance

Balanced dates use the 30%-risk last-frost date as the anchor. The Milwaukee planting calendar has typical and safe dates, fall planting and a month-by-month list for 26 vegetables.

When to plant tomatoes in Milwaukee · Fall planting dates for Milwaukee

Frost dates near Milwaukee

All Wisconsin cities

Frequently asked questions

What is the average last frost date in Milwaukee?

The typical (median, 50%) last 32°F night in Milwaukee is Apr 26, based on NOAA 1991–2020 normals at Mount Mary College. For a safer target, use May 12; after that, only about 1 year in 10 still has a freeze.

When is the first frost in Milwaukee?

Typically by Oct 18 for the first 32°F night, though about 1 year in 10 it comes as early as Oct 2. The first 36°F night (frost possible on plants) typically shows up around Oct 6.

What growing zone is Milwaukee, Wisconsin? Is Milwaukee zone 5 or 6?

Milwaukee is in USDA hardiness zone 5b–6a on the current 2023 map (zone 5–6 for short). On the older 2012 map, most of the city was 5b. That's why older references still say 'zone 5'.

Is it too early to plant in Milwaukee?

For frost-tender plants, yes if it's before Apr 26: until then, the odds of another 32°F night are better than even. Between Apr 26 and May 12, the risk falls from 50% to 10%. Cool-season crops like peas and lettuce can go in weeks earlier; see the planting calendar.

What temperature is a killing frost?

It depends on the crop. Tender plants such as tomatoes are killed by a light frost, which CSU Extension describes as 28–32°F; below 28°F is a heavy frost. We show NOAA odds for 36°F (frost possible on plants), 32°F (freeze, our headline) and 28°F (hard freeze).

Is first frost the same as first freeze?

Not quite. A 'freeze' means the air reached 32°F. 'Frost' is ice on surfaces, and it can form on calm, clear nights even when the air is a few degrees above freezing. So in Milwaukee, the first 36°F night (frost possible on plants) typically comes around Oct 6, before the first 32°F night (Oct 18).

Download & sources

• Add Milwaukee frost & planting dates to your calendar (.ics, 2027)
• Printable planting calendar (PDF)
• How these numbers are calculated

Data: NOAA NCEI U.S. Climate Normals 1991–2020 (annual/seasonal and daily normals, station USC00475474); USDA Plant Hardiness Zone ZIP tables 2023 and 2012 by the PRISM Group, Oregon State University; Census 2020 ZIP/place relationship file; USGS elevation. Long-term odds, not a forecast. Figures and sentences are generated from these data by fixed rules; see the methodology. Last updated 2026-10-08.