Bismarck Climate Trends
North Dakota · US States · 50 years of climate trend data
This page tracks how Bismarck's climate has shifted over 50 years of daily measurements, warmer summers, milder winters, and changes in rainfall, rather than current conditions. The two clearest signs of change: the growing season has grown 14 days longer and average winter temperatures have risen by 4.4°C. Measurement period: the last 50 years (1976-2025).
Data through September 12, 2026.
Frequently asked questions about Bismarck's climate
How much warmer have summers in Bismarck become?
The average daytime high across June, July and August rose by 0.9°C between 1976-1980 and 2021-2025. That is a five-year average at each end rather than two isolated summers, so a single exceptional heatwave or cool summer does not drive the number.
Have winters in Bismarck become milder?
The average daytime high across December, January and February rose by 4.4°C between 1976-1980 and 2021-2025. In many capitals in this dataset winter is changing faster than summer, which shows up most clearly in the frost-day count below.
How many days above 30°C does Bismarck get a year?
Bismarck averaged 26 days a year above 30°C in 2021-2025, up from 23 in 1976-1980. These are the days that set peak cooling demand and the days hospitals see heat complaints rise.
How many frost days does Bismarck still get?
Bismarck averaged 165 frost days a year in 2021-2025, up from 164 in 1976-1980. The frost count actually grew here, which is rare in this dataset.
Is spring arriving earlier in Bismarck?
Spring now starts about 2.4 weeks earlier than in 1976-1980. The start point is the first day the trailing seven-day average high crosses 12°C, a fixed in-house measure used only to compare Bismarck against itself rather than against other cities.
Has the growing season in Bismarck grown longer?
The growing season is about 14 days longer between 1976-1980 and 2021-2025. That is the stretch between the start of spring and the first autumn night below freezing, which is exactly the window gardens, farming and pollen seasons run inside.
Is rainfall in Bismarck getting heavier?
Bismarck averaged 6.4 days a year with more than 20mm of rain in 2021-2025, up from 3 in 1976-1980. Warmer air holds more water vapour, so the same annual rainfall increasingly arrives in shorter, harder bursts, which loads drains and water storage more than the annual total suggests.
