Climate Insights for Thermopolis

The climate in Thermopolis is cool. The average annual temperature is 7°C and approximately 356mm of precipitation falls per year. May is the wettest month, receiving around 75mm of rainfall. Thermopolis is in the Northern Hemisphere. Summer begins at the end of June and lasts through September. The summer months are: July, August, June. The coldest months are January, December, February, when temperatures can drop to -12°C. Snowfall occurs from January to December, with around 129cm accumulating over the season.

Thermopolis has a wide annual temperature range, spanning 43°C from the coldest to warmest months. The warmest month is July, when average highs reach 31°C and the mean temperature sits around 23°C. The coldest month is January, when overnight lows fall to -12°C and the daily average is -8°C. On average, daily temperatures fluctuate by about 14°C between overnight lows and afternoon highs. The sharpest temperature change occurs between September and October, with a 9°C shift in average temperatures.

Thermopolis is a quite dry location, receiving approximately 356mm of precipitation annually, which averages out to around 30mm per month. The wettest month is May, averaging 75mm of rainfall. April and September also tend to see above-average precipitation. The driest month is August, with just 11mm. That's 65mm less than May, the wettest month. Rainfall is heavily concentrated in certain months, creating a distinct wet and dry season. Visitors should plan around these patterns, as the difference between peak and low months is dramatic. Snowfall is a regular feature from January to December, with around 129cm accumulating over the season. April typically sees the most snow at around 24cm.

Thermopolis is relatively calm, with an average annual wind speed of 2km/h. For context, sustained winds below 12km/h are generally light, while anything above 25km/h is considered strong. The windiest month is April, averaging 3km/h, though still comfortable for most outdoor activities. The calmest conditions occur in November, with average winds dropping to 2km/h, making it an ideal period for wind-sensitive activities. Wind conditions are fairly consistent throughout the year, varying by only 1km/h between the calmest and windiest months.

It is currently summer in Thermopolis, which began on June 21, 2026. Thermopolis is in the Northern Hemisphere, where spring begins in March, summer in June, autumn in September, and winter in December. The warmest period peaks in July at around 31°C, while the coldest stretch bottoms out in January near -12°C. Autumn is next, beginning on September 23, 2026 — 70 days from now.

The best time to visit Thermopolis is during June, July, August and September, when the weather is most comfortable for travellers. During these months, average temperatures hover around 20°C with modest rainfall averaging 24mm per month. By contrast, January can be quite cold with temperatures dropping to -12°C. With minimal rainfall expected, you can pack light and plan outdoor activities with confidence.

The table below shows monthly climate averages for Thermopolis based on historical weather data. Min and max temperatures represent typical overnight lows and afternoon highs for each month, shown in degrees Celsius (°C). Precipitation is measured in millimetres (mm) and indicates the average total rainfall per month. Snow is measured in centimetres (cm) and reflects average monthly snowfall accumulation. Wind speed is the average sustained speed in kilometres per hour (km/h). All values are based on averages from over 10 years of historical weather data. The current month is highlighted for quick reference.