Frost dates / North Dakota / Bismarck

Frost dates in Bismarck, ND

The station on this page is BISMARCK 2.4 NNW, ND US (USC00320817), 1.8 miles from the city point. Population in the Census 2024 estimate is 77,772.

Zone 4aUSDA average annual extreme minimum -30°F to -25°F, from ZIP 58505 (0.7 miles from the city point used on this page).

Median last 32°F is May 10. Median first 32°F is September 30. The 50% growing-season length is 142 days. The green band runs from the median last frost to the median first frost. Thin ticks mark the 10%, 50%, and 90% dates.

Outside the median season Growing seasonTicks: 10%, 50%, and 90%

Last 32°F in spring

NCEI’s probability is the chance the last spring minimum of 32°F or lower occurs on or after the date.

Probability	Date	How to read it
90%	April 30	Earlier date. A last 32°F on or after this day is common.
50%	May 10	Median.
10%	May 23	Later date. A last 32°F on or after this day is uncommon.

First 32°F in fall

NCEI’s probability is the chance the first autumn minimum of 32°F or lower occurs on or before the date.

Probability	Date	How to read it
10%	September 16	Earlier date. A first 32°F on or before this day is uncommon.
50%	September 30	Median.
90%	October 13	Later date. A first 32°F on or before this day is common.

32°F growing-season length

Days between the last spring 32°F and the first autumn 32°F. The figure is a length the season meets or exceeds at that probability, from NCEI, not a subtraction done on this site.

Probability the season is at least this long	Days
10%	159
50%	142
90%	124

28°F threshold

	10%	50%	90%
Last, on or after	May 13	May 1	April 18
First, on or before	September 25	October 9	October 22
Season at least	179 days	161 days	140 days

36°F threshold

	10%	50%	90%
Last, on or after	June 2	May 20	May 8
First, on or before	September 8	September 21	October 4
Season at least	142 days	123 days	105 days

Station BISMARCK 2.4 NNW, ND US (USC00320817). Completeness flag R, 12 years used for the 32°F dates. NCEI’s annual probability of at least one day at or below 32°F is 100%. Freeze dates are conditional on that threshold occurring. Elevation 558.1 m. The same probability language applies to the 28°F and 36°F rows when those dates passed the same quality checks.

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Bismarck, ND

Zone 4aAverage annual extreme minimum -30°F to -25°F

Outside the median season Growing seasonTicks: 10%, 50%, and 90%

North Dakota. Nearest qualified station: BISMARCK 2.4 NNW, ND US (USC00320817), 1.8 miles. Median last 32°F May 10. Median first 32°F September 30. The 50% growing-season length is 142 days.

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32°F probabilities at this station

	10%	50%	90%
Last 32°F on or after	May 23	May 10	April 30
First 32°F on or before	September 16	September 30	October 13

Column order matches the NCEI file: for the last freeze, 10% is the later date and 90% is the earlier date. How to read the probabilities.

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Planting calendar

Frost dates for North Dakota are above. Planting windows appear for states with a cited extension guide. The fall and seed tools use the numbers you enter and the station dates.

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