Zone 3b Frost Dates and Planting Schedule

In USDA zone 3b, the typical last frost is May 16 and the typical first frost is September 26: the medians across its 157 ZIP codes, from NOAA 1991–2020 normals at the station nearest each one.

By HarvestMath Editors October 1, 2026 Share:

Typical first fall frost

Sep 26

range Sep 14 to Oct 2

Typical last spring frost

May 16

range May 8 to May 31

Median and 10th to 90th percentile across 157 ZIP codes in zone 3b, from each ZIP code's nearest NOAA station (1991–2020 normals). The spread is 23 days in spring.

A hardiness zone is a winter-cold rating: the average coldest night of the year. It doesn't predict when frost ends in spring. Two ZIP codes in zone 3b can be weeks apart on their last frost, so the dates here are a typical range, not your date.

Your exact frost dates

Find your dates by

US ZIP code

Enter a ZIP code or pick your hardiness zone to see your frost dates.

Zone 3b Planting Schedule

Typical for zone 3b, counted from the zone's typical May 16 last frost and Sep 26 first frost with the Season Planner's crop timing. Enter your ZIP code for your exact dates.

Typical for zone 3b

Mar 21–Apr 4 Start tomatoes indoors

Tomato seed needs 6 to 8 weeks under lights before it goes out.
Apr 4–Apr 18 Sow peas outdoors

Peas take cold soil and light frost in stride.
Apr 18–May 2 Sow leaf lettuce outdoors

Sow again every 2 to 3 weeks for a steady supply.
May 23–May 30 Transplant tomatoes and peppers

Once nights stay above 50°F.
May 23–May 30 Sow bush beans

Beans rot in cold soil: wait for 60°F at 4 inches deep.
Jul 4–Jul 18 Sow a fall crop

Kale, carrots, spinach or lettuce, 10 to 12 weeks before the first fall frost.
Oct 3–Oct 10 Plant garlic

Cloves go in 1 to 2 weeks after the first killing frost, for next summer.

Zone 3b Cities and Their Frost Dates

Same zone, different dates: each city's own station.

Zone 3b Frost FAQ

When is the last frost in zone 3b?

Typically around May 16, but it ranges from May 8 to May 31 across the zone's ZIP codes (10th to 90th percentile). Enter your ZIP code for your own station's date.

When is the first frost in zone 3b?

Typically around September 26, ranging September 14 to October 2 across zone 3b.

When do you plant tomatoes in zone 3b?

Typically May 23 to May 30, a week or two after the zone's typical last frost. Your own last frost can be weeks either side of that.

Neighboring Zones

Zone 3b covers ZIP codes in Minnesota.

A garden in a zone 3b climate — An illustration of a zone 3b garden.

Free book · 23 pages, PDF

The Spacing & Planting Cheat Sheet

When to start, when to plant, how far apart.