Last frost date in Mandan, ND

Average last frost
May 13

The average last frost in Mandan is May 13. By May 26 the chance of another 32°F night drops to 1 in 10. The first fall frost usually arrives about September 27, which leaves 136 frost-free days. An early freeze before September 15 happens one year in ten.

Safe after (10% risk)
May 26
Average first frost
Sep 27
Frost-free season
136 days
Hard freeze (28°F) ends
May 3
Next 7 nights in Mandan

Hard freeze likely Sat night, low 28°F

National Weather Service forecast, updated Oct 22, 12:57 UTC

  1. ThuOct 2256°
  2. FriOct 2343°
  3. SatOct 2428°hard freeze
  4. SunOct 2530°frost
  5. MonOct 2628°hard freeze
  6. TueOct 2734°possible frost
  7. WedOct 2831°frost
JanFebMarAprMayJunJulAugSepOctNovDecLast frost May 13First frost Sep 27136 frost-free daysBlue: chance of 32°F frost. Green: average frost-free season.JFMAMJJASOND136 frost-free days
Frost risk through the year at Mandan Experiment Station, 1.6 miles from Mandan.

Planting calendar for Mandan

Windows count forward or back from the average frost dates above. Click a crop for dates across North Dakota.

Start indoorsPlant outSow outdoorsFall plantingAverage last and first frost
Warm-season crops
JanFebMarAprMayJunJulAugSepOctNovDec
TomatoesMay 20–Jun 3
PumpkinsMay 27–Jun 10
SunflowersMay 13–Jun 3
CucumbersMay 27–Jun 3
CornMay 20–Jun 3
Sweet potatoesJun 3–Jun 17
WatermelonMay 27–Jun 10
Green beansMay 20–Jun 10
ZucchiniMay 20–Jun 3
OkraJun 3–Jun 17
PeppersMay 27–Jun 10
BasilMay 20–Jun 3
Butternut squashMay 20–Jun 3
CantaloupeMay 27–Jun 10
EggplantMay 27–Jun 10
Cool-season crops
JanFebMarAprMayJunJulAugSepOctNovDec
PotatoesApr 15–Apr 29
OnionsApr 1–Apr 22
CarrotsApr 22–May 27
LettuceApr 29–May 20
BroccoliApr 15–Apr 29
BeetsApr 15–May 27
PeasApr 1–Apr 15
CabbageApr 15–Apr 29
RadishesApr 8–May 20
Brussels sproutsApr 29–May 13
SpinachApr 1–Apr 22
CilantroApr 29–May 20
KaleApr 15–Apr 29
Collard greensApr 15–Apr 29
TurnipsApr 15–Apr 29
DillMay 13–May 27
CeleryMay 20–May 27
CauliflowerApr 29–May 13
LeeksApr 29–May 13
Swiss chardApr 29–May 27
ParsleyApr 29–May 20
Fall bulbs and garlic
JanFebMarAprMayJunJulAugSepOctNovDec
Tulip bulbsSep 13–Oct 18
GarlicSep 6–Oct 11
Daffodil bulbsAug 30–Oct 11
Perennials
JanFebMarAprMayJunJulAugSepOctNovDec
StrawberriesApr 15–Apr 29
AsparagusApr 15–Apr 29

Frost probabilities

ThresholdSpring, 90% chance laterSpring, 50%Spring, 10%Fall, 10% chance earlierFall, 50%Fall, 90%
Light frost, 32°FMay 1May 13May 26Sep 15Sep 27Oct 10
Hard freeze, 28°FApr 19May 3May 17Sep 23Oct 4Oct 19

Read the spring 10% column as the date after which only one year in ten still gets frost. That is the safer date for tomatoes, peppers and basil.

Where these numbers come from

NOAA station Mandan Experiment Station (USC00325479) sits 1.6 miles from the center of Mandan at 1,750 feet. Its averages cover 1991 to 2020. Low spots, valleys and open fields can keep getting frost a week or two after the station stops; city centers and lakeshores usually get less of it.

Questions

When is the last frost in Mandan, ND?

The average last frost date in Mandan is May 13, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after May 26.

When is the first frost in Mandan?

The first frost in fall usually comes around September 27. One year in ten it arrives before September 15.

How long is the growing season in Mandan?

About 136 days between the average last and first frost.

When should I plant tomatoes in Mandan?

Plant tomato seedlings outside from May 20 to June 3. Start seeds indoors six to eight weeks earlier.

Nearby in North Dakota

All 8 cities in North Dakota