Zone 4b Frost Dates & Planting Calendar

USDA Zone 4b has average coldest-winter lows of −25°F to −20°F. Across the 79 cities we track in this zone, the typical last spring frost is around May 5 and the typical first fall frost around October 4.

Winter low −25°F to −20°F

Typical last frost May 5

Typical first frost October 4

Cities 79

Hardiness zones describe winter cold, not frost timing (why that matters). For dates specific to your town, look up your ZIP code.

Zone 4b Planting Calendar

Vegetables
Crop	Start indoors	Direct sow	Transplant	Fall planting	Maturity	Notes
Tomato	Mar 10 – Mar 24	—	May 12 – May 19	—	60–85 days	Start indoors 6-8 weeks before last frost; transplant out 1-2 weeks after last frost once soil has warmed.
Pepper	Feb 24 – Mar 10	—	May 12 – May 26	—	60–90 days	Slow to germinate; start indoors 8-10 weeks before last frost. Transplant only once nights stay above 55F, 1-3 weeks after last frost.
Eggplant	Feb 24 – Mar 10	—	May 19 – May 26	—	65–85 days	Warm-season crop, similar timing to pepper; needs consistently warm soil (65F+) to transplant.
Cucumber	Apr 7 – Apr 14	May 12 – May 19	May 12 – May 19	—	50–65 days	Can be started indoors 3-4 weeks before transplanting, or direct-sown 1-2 weeks after last frost once soil is warm.
Zucchini	Apr 14 – Apr 21	May 12 – May 26	May 12 – May 19	—	45–55 days	Fast-growing squash; direct sow 1-3 weeks after last frost, or start indoors 2-3 weeks early for a head start.
Winter Squash	Apr 7 – Apr 14	May 12 – May 26	May 12 – May 19	—	80–110 days	Long season; direct sow after soil warms, or start indoors 3-4 weeks before last frost in short-season climates.
Pumpkin	—	May 12 – May 26	—	—	90–120 days	Direct sow 1-3 weeks after last frost; back-time from your first fall frost so the 90-120 day maturity window lands before it.
Watermelon	Apr 7 – Apr 14	—	May 19 – May 26	—	70–90 days	Needs warm soil (65F+); start indoors 3-4 weeks before last frost, transplant 2-3 weeks after last frost.
Cantaloupe	Apr 7 – Apr 14	—	May 19 – May 26	—	70–90 days	Same warm-soil requirements as watermelon; avoid disturbing roots when transplanting.
Corn	—	May 5 – May 19	—	—	60–100 days	Direct sow at last frost to 2 weeks after, once soil reaches 60F; does not transplant well. Succession sow every 2 weeks.
Green Bean	—	May 5 – May 19	—	—	50–65 days	Direct sow at last frost to 2 weeks after, once soil has warmed; frost-tender, do not rush.
Pea	—	Mar 24 – Apr 7	—	—	55–70 days	Cold-hardy; direct sow 4-6 weeks before last frost as soon as soil can be worked.
Lettuce	—	Apr 7 – Apr 21	—	Aug 9 – Aug 23	45–60 days	Cold-hardy; direct sow 2-4 weeks before last frost. Also transplantable from indoor starts.
Spinach	—	Mar 24 – Apr 7	—	Aug 9 – Aug 23	40–50 days	Very cold-hardy; direct sow 4-6 weeks before last frost as soon as soil can be worked.
Kale	—	Apr 7 – Apr 21	—	Jul 26 – Aug 9	50–65 days	Cold-hardy; direct sow 2-4 weeks before last frost or start indoors for earlier transplants.
Arugula	—	Apr 7 – Apr 21	—	Aug 23 – Aug 30	30–40 days	Fast-growing, cold-tolerant green; direct sow 2-4 weeks before last frost, succession sow every 2-3 weeks.
Swiss Chard	—	Apr 14 – Apr 28	—	—	50–60 days	Fairly cold-hardy; direct sow 1-3 weeks before last frost. Tolerates light frost in fall too.
Broccoli	Mar 17 – Mar 31	—	Apr 14 – Apr 21	Aug 2 – Aug 9	55–80 days	Start indoors 5-7 weeks before last frost; transplant out 2-3 weeks before last frost (hardens off to light frost).
Cauliflower	Mar 17 – Mar 31	—	Apr 21 – Apr 28	Jul 26 – Aug 2	55–85 days	Fussier than broccoli about temperature swings; start indoors 5-7 weeks before last frost, transplant 1-2 weeks before last frost.
Cabbage	Mar 17 – Mar 31	—	Apr 7 – Apr 21	Jul 26 – Aug 9	60–100 days	Cold-hardy; start indoors 5-7 weeks before last frost, transplant 2-4 weeks before last frost.
Brussels Sprouts	Mar 17 – Mar 31	—	Apr 14 – Apr 28	—	90–110 days	Long-season crop best timed to mature after a light fall frost for sweetest flavor; start indoors 5-7 weeks before last frost.
Carrot	—	Apr 7 – Apr 21	—	Jul 12 – Jul 26	60–80 days	Direct sow only (does not transplant); sow 2-4 weeks before last frost, as soon as soil can be worked.
Beet	—	Apr 7 – Apr 21	—	Jul 26 – Aug 9	50–65 days	Direct sow 2-4 weeks before last frost; tolerates light frost.
Radish	—	Mar 31 – Apr 14	—	Aug 23 – Sep 6	22–30 days	Very fast and cold-hardy; direct sow 3-5 weeks before last frost, as soon as soil can be worked.
Turnip	—	Apr 7 – Apr 21	—	Jul 26 – Aug 9	40–60 days	Cold-hardy; direct sow 2-4 weeks before last frost.
Onion	Feb 24 – Mar 10	—	Apr 7 – Apr 21	—	90–120 days	Start seeds indoors 8-10 weeks before last frost (or use sets/transplants); set out 2-4 weeks before last frost, very cold-tolerant as seedlings.
Garlic	—	—	—	Sep 6 – Sep 20	240–270 days	Fall-planted crop only; not planted in spring in most climates.
Potato	—	Apr 7 – Apr 21	—	—	70–120 days	Plant seed potatoes 2-4 weeks before last frost, as soon as soil can be worked and is above 45F; light frost on emerging foliage is usually tolerated.
Sweet Potato	—	—	May 19 – Jun 2	—	90–120 days	Set out slips 2-4 weeks after last frost once soil is thoroughly warm (65F+); very frost/cold sensitive.
Asparagus	—	—	Apr 7 – Apr 21	—	730–1095 days	Perennial; plant crowns 2-4 weeks before last frost as soon as soil can be worked. Takes 2-3 years to full production.

Herbs
Crop	Start indoors	Direct sow	Transplant	Fall planting	Maturity	Notes
Basil	Mar 24 – Mar 31	—	May 12 – May 19	—	50–70 days	Very frost/cold sensitive; start indoors 5-6 weeks before last frost, transplant only after all danger of frost (1-2 weeks after) and nights stay warm.
Cilantro	—	Apr 14 – Apr 28	—	Aug 9 – Aug 23	45–70 days	Cool-season, bolts in heat; direct sow 1-3 weeks before last frost, succession sow through spring.
Parsley	Mar 10 – Mar 24	—	Apr 21 – Apr 28	—	70–90 days	Slow to germinate; start indoors 6-8 weeks before last frost, transplant 1-2 weeks before last frost (biennial, cold-tolerant).
Dill	—	Apr 14 – Apr 28	—	—	40–60 days	Taprooted, does not transplant well; direct sow 1-3 weeks before last frost, succession sow through summer.
Oregano	Mar 10 – Mar 24	—	May 5 – May 12	—	80–90 days	Perennial herb; start indoors 6-8 weeks before last frost, transplant around/just after last frost date.
Thyme	Mar 10 – Mar 24	—	May 5 – May 12	—	85–95 days	Perennial herb, slow from seed; start indoors 6-8 weeks before last frost, transplant around/after last frost.

Flowers
Crop	Start indoors	Direct sow	Transplant	Fall planting	Maturity	Notes
Sunflower	—	May 12 – May 26	—	—	70–100 days	Direct sow 1-3 weeks after last frost once soil has warmed; taprooted, resents transplanting.
Zinnia	Apr 7 – Apr 14	May 12 – May 26	May 12 – May 19	—	60–70 days	Frost-tender; direct sow 1-3 weeks after last frost, or start indoors 3-4 weeks early for earlier blooms.
Marigold	Mar 24 – Apr 7	—	May 12 – May 19	—	45–60 days	Frost-tender; start indoors 4-6 weeks before last frost, transplant after all frost danger has passed.
Cosmos	Apr 7 – Apr 14	May 12 – May 26	May 12 – May 19	—	60–90 days	Easy from direct seed 1-3 weeks after last frost; can also start indoors 3-4 weeks early.
Nasturtium	—	May 12 – May 26	—	—	50–65 days	Frost-tender, resents root disturbance; direct sow 1-3 weeks after last frost once soil has warmed.
Dahlia	—	—	May 12 – May 26	—	90–120 days	Plant tubers 1-3 weeks after last frost once soil is warm (60F+); very frost-sensitive.

Date ranges are estimates based on university extension guidelines and this city's NOAA frost normals — not a guarantee. Scroll to see all columns on narrow screens.

Cities in Zone 4b

City	Last frost	First frost
Minneapolis, MN	Apr 23	Oct 16
Rochester, MN	Apr 30	Oct 6
Eau Claire, WI	Apr 24	Oct 14
Saint Cloud, MN	May 7	Sep 30
Lakeville, MN	Apr 27	Oct 10
Great Falls, MT	May 6	Oct 1
Wausau, WI	May 6	Oct 4
Andover, MN	May 5	Oct 2
Superior, WI	May 6	Oct 9
Ramsey, MN	May 4	Oct 5
Owatonna, MN	May 5	Oct 6
Prior Lake, MN	Apr 23	Oct 14
Chaska, MN	May 5	Oct 5
Austin, MN	Apr 30	Oct 5
Elk River, MN	May 4	Oct 5
Dickinson, ND	May 20	Sep 22
Brookings, SD	May 6	Oct 1
Faribault, MN	May 5	Oct 5
Watertown, SD	May 7	Sep 30
Northfield, MN	May 5	Oct 5
Willmar, MN	Apr 30	Oct 7
Forest Lake, MN	May 3	Oct 5
Stillwater, MN	Apr 22	Oct 19
Marshfield, WI	May 5	Oct 5
Wisconsin Rapids, WI	May 9	Sep 30
Sartell, MN	May 7	Sep 30
Red Wing, MN	Apr 23	Oct 14
Saint Michael, MN	May 4	Oct 5
Menomonie, WI	May 9	Oct 1
Ham Lake, MN	May 5	Oct 2
Buffalo, MN	Apr 30	Oct 9
Otsego, MN	May 4	Oct 5
Jamestown, ND	May 8	Sep 29
River Falls, WI	May 11	Oct 1
Weston, WI	May 6	Oct 4
Hugo, MN	Apr 23	Oct 20
Pierre, SD	May 6	Oct 3
Chippewa Falls, WI	May 8	Oct 4
Hutchinson, MN	Apr 28	Oct 8
Sault Ste. Marie, MI	May 9	Oct 11

States with Zone 4b cities

Frequently Asked Questions

What is the temperature range for Zone 4b?

Zone 4b is defined by an average annual extreme minimum winter temperature of −25°F to −20°F (USDA 2023 Plant Hardiness Zone Map).

When is the last frost in Zone 4b?

Typically around May 5, though it varies by location. Hardiness zones measure winter cold, not frost timing, so two places in the same zone can have last frosts weeks apart — check your city's page for local dates.

When is the first frost in Zone 4b?

Typically around October 4 across the cities we track in Zone 4b.

Neighboring zones: Zone 4a · Zone 5a · All zones