Last spring frost: April 25 (50% probability)
First fall frost: October 19 (50% probability)
Frost-free growing season: 177 days
Approximate USDA zone: 6a
The median last spring frost date for Milwaukee, WI (ZIP code 53205) is around April 25. This is the 50th-percentile date — meaning half of all years see frost end before this date. Use the 10% and 90% dates to understand the full range of risk in your area.
The median first fall frost date for Milwaukee, WI is around October 19. Plan to harvest or protect frost-sensitive crops like tomatoes and peppers at least a week before this date to avoid losses.
The frost-free growing season in Milwaukee is about 177 days. This window — from your last spring frost to your first fall frost — is when warm-season vegetables thrive. Cold-hardy crops like kale, spinach, and peas can extend your season by weeks on either side.
Based on frost date patterns, Milwaukee falls approximately in 6a. USDA hardiness zones are determined by average annual minimum winter temperatures and guide both plant selection and planting timing for your location.
Start tomato seeds indoors 6–8 weeks before your last frost date (around April 25). That means starting in late July 25 or early August 25 for Milwaukee. Transplant outdoors 1–2 weeks after your last frost.