Climate - Helena (Montana)
Average weather, temperature, rainfall, sunshine hours
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Climate chart - Helena (Montana)
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.
Helena - Average temperatures (1991-2020) | Month | Min (°C) | Max (°C) | Mean (°C) | Min (°F) | Max (°F) | Mean (°F) |
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| January | -10.3 | 0.2 | -5 | 14 | 32 | 23 |
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| February | -8.2 | 2.9 | -2.7 | 17 | 37 | 27.2 |
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| March | -4.1 | 8.6 | 2.2 | 25 | 48 | 36 |
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| April | 0.2 | 13.7 | 7 | 32 | 57 | 44.6 |
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| May | 5.3 | 19.1 | 12.2 | 42 | 66 | 54 |
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| June | 9.3 | 23.7 | 16.5 | 49 | 75 | 61.7 |
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| July | 12.8 | 30.1 | 21.4 | 55 | 86 | 70.6 |
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| August | 11.6 | 29.2 | 20.4 | 53 | 85 | 68.8 |
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| September | 7 | 22.9 | 15 | 45 | 73 | 59 |
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| October | 0.8 | 14.2 | 7.5 | 34 | 58 | 45.6 |
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| November | -5.1 | 6 | 0.4 | 23 | 43 | 32.8 |
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| December | -9.9 | 0.3 | -4.8 | 14 | 33 | 23.4 |
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| Year | 0.8 | 14.3 | 7.55 | 33.5 | 57.8 | 45.5 |
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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.
Helena - Average precipitation| Month | Millimeters | Inches | Days |
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| January | 10 | 0.4 | 6 |
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| February | 10 | 0.4 | 6 |
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| March | 15 | 0.6 | 7 |
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| April | 25 | 1 | 9 |
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| May | 50 | 2 | 11 |
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| June | 55 | 2.2 | 12 |
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| July | 25 | 1 | 8 |
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| August | 25 | 1 | 6 |
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| September | 25 | 1 | 6 |
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| October | 20 | 0.8 | 7 |
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| November | 15 | 0.6 | 6 |
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| December | 10 | 0.4 | 7 |
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| Year | 290 | 11.4 | 91 |
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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.
Helena - Sunshine hours| Month | Average | Total |
|---|
January | 4 | 120 | February | 5.5 | 150 | March | 7.5 | 225 | April | 8 | 245 | May | 9 | 280 | June | 10.5 | 310 | July | 12 | 370 | August | 10.5 | 325 | September | 8.5 | 255 | October | 6.5 | 205 | November | 4 | 120 | December | 3 | 100 | Year | 7.4 | 2700 |
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.
Helena - Weather by month
Based on the period 1991-2020
January, the coldest month of the year, is generally a very cold month. The average temperature is of -5.0 °C (23 °F), with a minimum of -10.3 °C (13.5 °F) and a maximum of 0.2 °C (32.4 °F).
On the coldest nights of the month, the temperature usually drops to around -24.5 °C (-12.5 °F). However, it dropped to -38.4 °C (-37.1 °F) in January 1996.
On the warmest days of the month, the temperature usually reaches around 11.5 °C (53 °F). However, it reached 17.2 °C (63 °F) in January 2015.
Precipitation amounts to 10 mm (0.4 in), distributed over 6 days.
The day lasts on average 9 hours and 5 minutes.
There are on average 4 hours of sunshine per day. So, the sun shines 42% of the time.
The average humidity is 69%.
The average wind speed is 9 kph (6 mph).
February is generally a very cold month. The average temperature is of -2.7 °C (27 °F), with a minimum of -8.2 °C (17.2 °F) and a maximum of 2.9 °C (37.2 °F).
On the coldest nights of the month, the temperature usually drops to around -20.5 °C (-5 °F). However, it dropped to -40.6 °C (-41.1 °F) in February 1996.
On the warmest days of the month, the temperature usually reaches around 13 °C (56 °F). However, it reached 20.6 °C (69.1 °F) in February 1995.
Precipitation amounts to 10 mm (0.4 in), distributed over 6 days.
The day lasts on average 10 hours and 25 minutes.
There are on average 5.5 hours of sunshine per day. So, the sun shines 51% of the time.
The average humidity is 64%.
The average wind speed is 10 kph (6 mph).
March is generally a cold month. The average temperature is of 2.2 °C (36 °F), with a minimum of -4.1 °C (24.6 °F) and a maximum of 8.6 °C (47.5 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around -15.5 °C (4 °F). However, it dropped to -34.4 °C (-29.9 °F) in March 2019.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 19.5 °C (66.5 °F). However, it reached 25.6 °C (78.1 °F) in March 2004.
Precipitation amounts to 15 mm (0.6 in), distributed over 7 days.
The day lasts on average 12 hours and 0 minutes.
There are on average 7.5 hours of sunshine per day. So, the sun shines 61% of the time.
The average humidity is 57%.
The average wind speed is 12 kph (7 mph).
April is generally a quite mild month. However, there are remarkable differences between night and day. The average temperature is of 7.0 °C (45 °F), with a minimum of 0.2 °C (32.4 °F) and a maximum of 13.7 °C (56.7 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around -7.5 °C (18 °F). However, it dropped to -16.1 °C (3 °F) in April 2002.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 24.5 °C (76.5 °F). However, it reached 30 °C (86 °F) in April 1992.
Precipitation amounts to 25 mm (1 in), distributed over 9 days.
The day lasts on average 13 hours and 40 minutes.
There are on average 8 hours of sunshine per day. So, the sun shines 59% of the time.
The average humidity is 52%.
The average wind speed is 13 kph (8 mph).
May is generally a mild month. However, there are remarkable differences between night and day. The average temperature is of 12.2 °C (54 °F), with a minimum of 5.3 °C (41.5 °F) and a maximum of 19.1 °C (66.4 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around -2 °C (28 °F). However, it dropped to -6.7 °C (19.9 °F) in May 1996.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 29 °C (84 °F). However, it reached 33.9 °C (93 °F) in May 2001.
Precipitation amounts to 50 mm (2 in), distributed over 11 days.
The day lasts on average 15 hours and 5 minutes. So the days are long.
There are on average 9 hours of sunshine per day. So, the sun shines 60% of the time.
The average humidity is 51%.
The average wind speed is 13 kph (8 mph).
June is generally a very mild month. However, there are remarkable differences between night and day. The average temperature is of 16.5 °C (62 °F), with a minimum of 9.3 °C (48.7 °F) and a maximum of 23.7 °C (74.7 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 3 °C (37.5 °F). However, it dropped to -0.6 °C (30.9 °F) in June 1995.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 33 °C (92 °F). However, it reached 39.4 °C (102.9 °F) in June 2015.
Precipitation amounts to 55 mm (2.2 in), distributed over 12 days.
The day lasts on average 15 hours and 50 minutes. So the days are long. June 21, the summer solstice, is the longest day of the year in the Northern Hemisphere.
There are on average 10.5 hours of sunshine per day. So, the sun shines 65% of the time.
The average humidity is 50%.
The average wind speed is 13 kph (8 mph).
July, the warmest month of the year, is generally a warm month. However, there are remarkable differences between night and day. The average temperature is of 21.4 °C (71 °F), with a minimum of 12.8 °C (55.1 °F) and a maximum of 30.1 °C (86.1 °F).
On the coldest nights of the month, the temperature usually drops to around 7.5 °C (45.5 °F). However, it dropped to 2.8 °C (37 °F) in July 1995.
On the warmest days of the month, the temperature usually reaches around 36.5 °C (98 °F). However, it reached 40.6 °C (105.1 °F) in July 2002.
Precipitation amounts to 25 mm (1 in), distributed over 8 days.
The day lasts on average 15 hours and 25 minutes. So the days are long.
There are on average 12 hours of sunshine per day. So, the sun shines 77% of the time.
The average humidity is 41%.
The average wind speed is 11 kph (7 mph).
August is generally a warm month. However, there are remarkable differences between night and day. The average temperature is of 20.4 °C (69 °F), with a minimum of 11.6 °C (52.9 °F) and a maximum of 29.2 °C (84.6 °F).
On the coldest nights of the month, the temperature usually drops to around 6 °C (42.5 °F). However, it dropped to -2.2 °C (28 °F) in August 1992.
On the warmest days of the month, the temperature usually reaches around 36 °C (97 °F). However, it reached 39 °C (102.2 °F) in August 2001.
Precipitation amounts to 25 mm (1 in), distributed over 6 days.
The day lasts on average 14 hours and 5 minutes. So the days are long.
There are on average 10.5 hours of sunshine per day. So, the sun shines 74% of the time.
The average humidity is 41%.
The average wind speed is 10 kph (6 mph).
September is generally a very mild month. However, there are remarkable differences between night and day. The average temperature is of 15.0 °C (59 °F), with a minimum of 7 °C (44.6 °F) and a maximum of 22.9 °C (73.3 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around -0.5 °C (31 °F). However, it dropped to -7.2 °C (19 °F) in September 2000.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 33 °C (91 °F). However, it reached 36.1 °C (97 °F) in September 2007.
Precipitation amounts to 25 mm (1 in), distributed over 6 days.
The day lasts on average 12 hours and 30 minutes.
There are on average 8.5 hours of sunshine per day. So, the sun shines 68% of the time.
The average humidity is 48%.
The average wind speed is 10 kph (6 mph).
October is generally a quite mild month. However, there are remarkable differences between night and day. The average temperature is of 7.5 °C (46 °F), with a minimum of 0.8 °C (33.5 °F) and a maximum of 14.2 °C (57.6 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around -9 °C (15.5 °F). However, it dropped to -22.2 °C (-8 °F) in October 1991.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 26.5 °C (79.5 °F). However, it reached 31 °C (87.8 °F) in October 1997.
Precipitation amounts to 20 mm (0.8 in), distributed over 7 days.
The day lasts on average 10 hours and 50 minutes.
There are on average 6.5 hours of sunshine per day. So, the sun shines 60% of the time.
The average humidity is 57%.
The average wind speed is 10 kph (6 mph).
November is generally a cold month. The average temperature is of 0.4 °C (33 °F), with a minimum of -5.1 °C (22.8 °F) and a maximum of 6 °C (42.8 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around -17 °C (1.5 °F). However, it dropped to -25 °C (-13 °F) in November 1991.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 17.5 °C (63.5 °F). However, it reached 24 °C (75.2 °F) in November 1999.
Precipitation amounts to 15 mm (0.6 in), distributed over 6 days.
The day lasts on average 9 hours and 25 minutes.
There are on average 4 hours of sunshine per day. So, the sun shines 42% of the time.
The average humidity is 63%.
The average wind speed is 10 kph (6 mph).
December is generally a very cold month. The average temperature is of -4.8 °C (23 °F), with a minimum of -9.9 °C (14.2 °F) and a maximum of 0.3 °C (32.6 °F).
On the coldest nights of the month, the temperature usually drops to around -22.5 °C (-8.5 °F). However, it dropped to -33.3 °C (-27.9 °F) in December 2016.
On the warmest days of the month, the temperature usually reaches around 12 °C (54 °F). However, it reached 17.2 °C (63 °F) in December 1999.
Precipitation amounts to 10 mm (0.4 in), distributed over 7 days.
The day lasts on average 8 hours and 35 minutes. December 21, the winter solstice, is the shortest day of the year in the Northern Hemisphere.
There are on average 3 hours of sunshine per day. So, the sun shines 38% of the time.
The average humidity is 68%.
The average wind speed is 9 kph (6 mph).
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