Climate - Helena (Montana)

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The climate of Helena is arid continental, with very cold, snowy winters and warm summers, but with strong temperature variations and cool nights.
The city is the capital of the state of Montana and is located in the north-west of the United States, in the easternmost part of the Rocky Mountains, in a valley at 1,200 meters (3,900 feet) above sea level. A few miles away, in the same valley, flows the Missuori River, while to the east we find the Helena National Forest.
The climate is characterized by strong temperature changes between day and night, as well as by rapid changes in weather and temperature, depending on the prevailing air mass.
Another feature of Helena's climate is the Chinook, the warm, dry wind that blows from the Rocky Mountains, and is capable of raising the temperature by several degrees.
The average temperature of the coldest month (January) is of -5 °C (23 °F), that of the warmest month (July) is of 21.4 °C (71 °F). Here are the average temperatures.

Precipitation amounts to 290 millimeters (11.4 inches) per year: it is therefore scarce. It ranges from 10 mm (0.4 in) in the driest months (January, February, December) to 55 mm (2.2 in) in the wettest (June). Here is the average precipitation.

During the winter, sometimes as early as mid-November, colding spells can occur, in which the temperature drops to -30 °C (-22 °F) or less. The record is -41 °C (-42 °F), set in January 1957 and February 1996.
However, there are also sunny and quite mild periods, in which the temperature drops slightly below freezing at night, and exceeds 10 °C (50 °F) during the day.
Snowfalls in Helena are frequent, and can occur for a long period of the year, but are generally light due to the scarcity of precipitation. On average, 94 centimeters (37,2 in) of snow fall per year. It usually snows from October through April, but sometimes it can snow even in May and September. In 1992, it snowed on August 23.
Summer is sunny, with some afternoon thunderstorms. It is generally cool at night and hot during the day: between night and day, there are almost 20 degrees Celsius of difference (and sometimes even more). Given the high daily temperature range, even during the hottest periods, nights remain cool or at least acceptable.
On the hottest days of the year, the temperature typically reaches 37/38 °C (99/100 °F). The record is 40.5 °C (105 °F), recorded in July 2002 and August 1969.



On average, there are around 2,700 sunshine hours per year. Therefore, the amount of sunshine is very good. Here are the average sunshine hours per day.

Best Time

The best times to visit Helena are spring and autumn, and in particular the months of May and September, to avoid both the winter cold and the summer heat. However, at night it can get cold even in these months.