When is the last frost in Bismarck, ND?

The average last spring frost (50% probability of 32°F) in Bismarck is around May 14, based on NOAA/NCEI 1991–2020 normals at the Bismarck Wfo, ND station (4.2 mi away). Half of years it falls outside that date, so wait 1–2 weeks past it before setting out frost-tender plants.

When is the first fall frost in Bismarck?

The average first fall frost in Bismarck, ND is around September 30, giving roughly a 138-day frost-free growing season.

What planting zone is Bismarck, ND?

Bismarck is in USDA plant hardiness zone 4a (average annual extreme minimum temperature -30 to -25°F), from the 2023 USDA Plant Hardiness Zone Map.

What is the weather like in Bismarck?

In Bismarck, ND the warmest month is July (avg high 84.7°F) and the coldest is January (avg low 2.4°F). It averages about 19.1″ of precipitation a year and 50.5″ of snow.

Home › North Dakota › Bismarck

Bismarck, ND Planting Calendar & Frost Dates

USDA hardiness zone 4a · ZIP 58501 · elevation 505′ · NOAA & USDA data

Bismarck is in USDA hardiness zone 4a (winters can dip to -30 to -25°F), with a growing season of about 138 days between the average last spring frost (May 14) and first fall frost (September 30). The warmest month is July (avg high 84.7°F); the coldest is January (avg low 2.4°F). It averages 19.1″ of precipitation a year and 50.5″ of snow, mostly mid-winter. Start cool-season crops several weeks before the last frost; wait until after it for tomatoes, peppers and other tender crops.

Hardiness zone

min temp -30 to -25°F

Last spring frost

May 14

avg (50% prob, 32°F)

First fall frost

September 30

avg (50% prob, 32°F)

Growing season

138 days

frost-free window

Warmest month

July

avg high 84.7°F

Month-by-month typical weather in Bismarck

Average conditions from the NOAA/NCEI 1991–2020 U.S. Climate Normals at Bismarck, ND (4.2 mi away). Temperatures °F, precipitation & snow in inches.

Month	Avg high	Avg low	Mean	Precip (in)	Snow (in)
January	23.2	2.4	12.8	0.5	8.9
February	27.8	7.2	17.5	0.5	7.5
March	41	19.1	30.1	0.8	8.5
April	56	30.4	43.2	1.3	4.6
May	68.3	42.4	55.3	2.5	0.4
June	77.9	52.9	65.4	3.4	0
July	84.7	57.9	71.3	3.1	0
August	83.5	55.7	69.6	2.5	0
September	73.4	45.9	59.7	1.7	0
October	57.1	32.6	44.8	1.4	2.5
November	40.6	19.1	29.9	0.7	8
December	27.7	8.1	17.9	0.6	10.1

What to plant when in Bismarck

Crop	Season	What to do & when
Tomatoes	warm	Start seeds indoors: April 2 · Transplant out: May 21
Peppers	warm	Start seeds indoors: March 19 · Transplant out: May 28
Cucumbers	warm	Direct sow: May 21
Zucchini / squash	warm	Direct sow: May 21
Bush beans	warm	Direct sow: May 21
Sweet corn	warm	Direct sow: May 21
Basil	warm	Transplant out: May 21
Peas	cool	Sow (spring): April 9 · Sow (fall): August 5
Spinach	cool	Sow (spring): April 2 · Sow (fall): August 5
Lettuce	cool	Sow (spring): April 16 · Sow (fall): August 5
Kale	cool	Transplant (spring): April 23 · Sow (fall): July 22
Broccoli	cool	Transplant (spring): April 30
Carrots	cool	Sow (spring): April 23 · Sow (fall): July 22
Onions	cool	Transplant (spring): April 16
Potatoes	cool	Plant seed potatoes: April 30
Radishes	cool	Sow (spring): April 16 · Sow (fall): August 19

Dates are computed from Bismarck's average frost dates using standard cool-/warm-season timing. They're a starting point — a cold spring, a warm microclimate, or a fast-maturing variety can shift them by a week or two.

Want the exact dates for your yard? →
Look up your precise ZIP-code frost dates and a full 26-crop planting calendar on our free interactive tool.
Open the frost & planting tool

🌾 Get a frost reminder

One email in early spring and early fall with the dates for your area. No spam.

Gear that helps you plant on time

Some links below are Amazon affiliate links (tag theboringthin-20). If you buy through them we may earn a small commission at no extra cost to you — it keeps this almanac free. We only list generic, genuinely-useful categories.

Soil thermometer →Know when the ground is warm enough to sow — the honest signal, not the calendar.Seed-starting trays + dome →Start tomatoes & peppers indoors on the schedule below.Seedling heat mat →Warms the soil for faster, more even germination indoors.Floating row cover / frost cloth →Buys you 4–8°F to beat an early or late frost.Raised garden bed kit →Warms and drains faster in spring than in-ground soil.Garden gloves →Basic kit for transplant day.

Nearby cities in North Dakota

Minot, ND Grand Forks, ND Fargo, ND

Sources & method. Hardiness zone: 2023 USDA Plant Hardiness Zone Map (PRISM Climate Group, Oregon State University). Frost dates & growing season: NOAA/NCEI 1991–2020 U.S. Climate Normals, nearest station with published freeze normals — Bismarck Wfo, ND, 4.2 mi (confidence: high). Monthly weather normals: Bismarck, ND, 4.2 mi (confidence: high). ZIP centroid from U.S. Census 2023 ZCTA data. Frost dates are the 50%-probability date — half of years frost occurs outside the stated date. Nothing here is invented; where the nearest station is far, we say so. Last updated 2026-07-22.