Climate and monthly weather forecast
Longmont, CO

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The climate of Longmont

Longmont, situated in Colorado, USA, experiences a predominate Mid-latitude steppe climate as per the Köppen climate classification (BSk). This climate type indicates that Longmont is characterized by hot, sometimes extremely hot summers and cold, sometimes very cold and arid winters.

An overview of climatic parameters reveals a varied temperature span. The year usually starts and ends with the lower temperatures (from 21.2°F (-6°C) to 40.1°F (4.5°C) in January, and from 19.9°F (-6.7°C) to 39°F (3.9°C) in December). A steady rise in temperature occurs from February (from 20.8°F (-6.2°C) to 40.3°F (4.6°C)) to July, marking the peak of summer, when the minimum and maximum temperatures are 59.2°F (15.1°C) and 85.6°F (29.8°C), respectively. Subsequently, the temperature gradually declines towards the end of the year.

Rainfall patterns in Longmont are not constant throughout the year. The city experiences the least rainfall in January and December with 0.35" (9mm) and 0.39" (10mm), respectively. The maximum rainfall occurs in May, recording an average of 1.69" (43mm). By contrast, Snowfall is observed from January to April and again from October to December, with January recording the highest snowfall at 2.64" (67mm). Regarding general atmospheric conditions, relative humidity ranges between 42% to 66%, and air pressure varies minimally around a mean of 30" (762mm).

The best time to visit Longmont

Visitors who enjoy mild temperatures with moderate rainfall can choose to visit Longmont between May and June when the average high temperature varies from 66.4°F (19.1°C) to 81.1°F (27.3°C), rainfall hovers around 1.69" (43mm) to 0.94" (24mm), and daylight hours are abundantly available between 14.4 hours to 15 hours per day. Sunshine hours also peak in June, offering 11.9 hours of sunshine per day, thus making it a favorable period for out-of-door activities.

The worst time to visit Longmont

Conversely, for those sensitive to cold, the period from December to February may prove to be uncomfortable. During this period, the lowest temperature drops to 19.9°F (-6.7°C) and the maximum temperature struggles to reach 40.3°F (4.6°C). This period also records the highest snowfall, from 2.64" (67mm) in January to 3.9" (99mm) in February, which could pose challenges to travel.

Spring weather in Longmont

Spring in Longmont, occurring from March to May, brings a mixed bag of weather conditions. The temperature during this season ranges from 29.7°F (-1.3°C) to 66.4°F (19.1°C). An ever-increasing amount of rainfall is observed as Spring progresses, with rainfall increasing from 0.83" (21mm) in March to 1.69" (43mm) in May.

Summer weather in Longmont

Summer, which spans from June to August, sees the temperature reaching from 54.3°F (12.4°C) to 85.6°F (29.8°C). These months are relatively dry, with an average rainfall from 0.94" (24mm) to 1.54" (39mm). However, the month of June is the period of maximum sunlight with an average of 15 daylight hours and 11.9 sunshine hours per day.

Autumn weather in Longmont

Autumn weather, which spreads from September to November, returns to cooler temperatures, with the thermometer dipping from 51.1°F (10.6°C) in September to 29.1°F (-1.6°C) by the end of November. Rainfall reduces in this period to an average of 0.63" (16mm) in November, and daylight hours come down to 10 hours per day.

Winter weather in Longmont

Winter, from December to February, is marked by a sharp drop in temperature leading to cold to further colder weather. December witnesses a range in temperature from 19.9°F (-6.7°C) to 39°F (3.9°C), gradually increasing to a range from 20.8°F (-6.2°C) to 40.3°F (4.6°C) in February. During this period, Longmont experiences significant snowfall, peaking at 3.9" (99mm) in February, and minimum daylight hours averaging 9.7 in December to 10.7 in February.

Weather in January

Transitioning from the cold end of the previous year, January in Longmont, Colorado, continues to experience similarly frigid conditions. With an average high temperature of 40.1°F (4.5°C) and a chilly low of 21.2°F (-6°C), Longmont embraces the warmth of winter wear. Weather in January »

Weather in February

Rolling into February, Longmont still retains its cold weather, though not as intense as its predecessor and successor. A slightly higher snowfall amount of 3.9" (99mm) is notable during the month, spread across an average of 7.7 snowy days. Weather in February »

Weather in March

March marks the onset of spring in Longmont, with the weather transitioning from the chilly tones of winter to more temperate conditions. However, the city still experiences an occasional dusting of snow, though not as significant as the preceding months. Weather in March »

Weather in April

In April, Longmont experiences a noticeable increase in temperatures, symbolizing the true commencement of the spring season. While rare, the month is not devoid of white powder with records of 4.29" (109mm) of snow falling over an average of 3.3 days. Weather in April »

Weather in May

May is a clear departure from the cooling confines of winter and an open invitation to pleasant spring weather in Longmont. This month experiences the highest recorded rainfall of the year, accumulating to 1.69" (43mm) spread over an average of 15 days. Weather in May »

Weather in June

June brings with it the start of the summer season and warmer temperatures in Longmont. The transition from spring to summer is marked with decreased rainfall, registering at 0.94" (24mm) distributed over 11.2 days. It's an ideal period to indulge in outdoor excursions as June boasts extended daylight hours and sunny weather, thrilling both residents and visitors. Weather in June »

Weather in July

July is the zenith of the summer season in Longmont, reflecting the highest temperatures and peak solar intensity. Weather conditions, not surprisingly, indicate an increase in rainfall to 1.54" (39mm), which spans an average of 16 days. Weather in July »

Weather in August

August presents another month of the summer season in Longmont with the temperature slightly decreasing compared to July, yet still maintaining a strong hold on the warmth. Rainfall slightly decreases to 0.98" (25mm) over 13.3 days, indicating a transition towards the impending autumn season. Weather in August »

Weather in September

September signals the onset of the autumn season in Longmont, with temperatures diminishing distinctly from the earlier summer highs. The weather remains pleasant and rainfall levels decrease to 0.75" (19mm), falling over an average of 9.7 days. Weather in September »

Weather in October

Entering October, Longmont sees the beauty of fall in all its glory. This month marks a significant decrease in temperatures, veering towards the colder side of the year. The falling leaves and shorter days hint toward the incoming winter season, with rainfall settling at 0.67" (17mm) over 5.9 days. Weather in October »

Weather in November

November in Longmont witnesses the transition from autumn towards the colder winter season. The temperature falls noticeably, and snowfall returns with a total of 4.41" (112mm) scattered over 5.4 days, creating a stark contrast to the previous months. Weather in November »

Weather in December

December manifests the winter season in its entire splendor in Longmont. As temperatures drop further, the city experiences an increment in snow accumulation up to 3.03" (77mm) over 6.1 days relative to its predecessor. As the year concludes, the city gleams under the holiday lights, reclining under a fresh blanket of snow. Weather in December »
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Frequently asked questions

What is the driest month in Longmont?

January is the month with the least rainfall in Longmont. Rain falls for 3.5 days and accumulates 0.35" (9mm) of precipitation.

How many days does it rain in Longmont?

Throughout the year, there are 105.4 rainfall days, and 10.43" (265mm) of precipitation is accumulated.

When does it snow in Longmont?

Months with snowfall are January through May, October through December.

How many days does it snow in Longmont?

In Longmont, during the entire year, snow falls for 37.1 days and aggregates up to 26.73" (679mm) of snow.

What is the month with the lowest UV index in Longmont?

January, February, November and December, with an average maximum UV index of 2, are months with the lowest UV index.

What is the most humid month in Longmont?

The most humid month is February, with an average relative humidity of 66%.

What is the month with the least sunshine in Longmont?

The month with the least sunshine is February, with an average of 6.8h of sunshine.

When is Daylight Saving Time (DST) in Longmont?

On Sunday, March 10. 2024, at 2:00 am, Daylight Saving Time starts in Longmont, and the time zone changes from MST to MDT. Daylight Saving Time ends Sunday, November 3. 2024, at 2:00 am, and the time zone reverts from MDT to MST.

What is the rainiest month in Longmont?

May is the month with the most rainfall in Longmont. Rain falls for 15 days and accumulates 1.69" (43mm) of precipitation.

When it does not snow in Longmont?

In Longmont, snow does not fall in June through September.

When are the longest days in Longmont?

With an average of 15h and 0min of daylight, June has the longest days of the year.

What month has the most sunshine in Longmont?

With an average of 11.9h of sunshine, June has the most sunshine of the year.

What is the hottest time of year in Longmont?

July tends to be the warmest month, with temperatures averaging a daily high of 85.6°F (29.8°C) and a low of 59.2°F (15.1°C).

What is the month with the highest UV index in Longmont?

July and August, with an average maximum UV index of 6, are months with the highest UV index in Longmont.

What is the least humid month in Longmont?

August is the least humid month in Longmont, with an average relative humidity of 42%.

When does it snow the most in Longmont?

The month with the most snowfall in Longmont is November, when snow falls for 5.4 days and typically aggregates up to 4.41" (112mm) of snow.

What are the coldest months in Longmont?

Longmont's coldest month, December, registers temperatures that range from a high of 39°F (3.9°C) to a low of 19.9°F (-6.7°C).

What is the month with the shortest days in Longmont?

December has the shortest days of the year, with an average of 9h and 24min of daylight.

Average temperature
Longmont, CO

Average temperature - Longmont, CO

The warmest month (with the highest average high temperature) is July (85.6°F).
The month with the lowest average high temperature is December (39°F).

The month with the highest average low temperature is July (59.2°F).
The coldest month (with the lowest average low temperature) is December (19.9°F).

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Average pressure
Longmont, CO

Average pressure - Longmont, CO

The month with the highest atmospheric pressure is January (30.15"Hg).
The months with the lowest atmospheric pressure are April and June (29.91"Hg).

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Average wind speed
Longmont, CO

Average wind speed - Longmont, CO

The windiest months (with the highest average wind speed) are March and April (6.6mph).
The calmest months (with the lowest average wind speed) are August and September (5.6mph).

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Average rainfall
Longmont, CO

Average rainfall - Longmont, CO

The wettest month (with the highest rainfall) is May (1.69").
The driest month (with the least rainfall) is January (0.35").

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Average rainfall days
Longmont, CO

Average rainfall days - Longmont, CO

The month with the highest number of rainy days is July (16 days).
The month with the least rainy days is January (3.5 days).

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Average snowfall
Longmont, CO

Average snowfall - Longmont, CO

The month with the highest snowfall is November (4.41").
The months with the least snowfall are June, July, August and September (0").

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Average snowfall days
Longmont, CO

Average snowfall days - Longmont, CO

The month with the highest number of snowfall days is February (7.7 days).
The months with the least snowfall days are June, July and August (0 days).

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Average daylight / Average sunshine
Longmont, CO

Average daylight / Average sunshine - Longmont, CO

The month with the longest days is June (Average daylight: 15h and 0min).
The month with the shortest days is December (Average daylight: 9h and 24min).

The month with the most sunshine is June (Average sunshine: 11h and 54min).
The month with the least sunshine is February (Average sunshine: 6h and 48min).

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Average sunshine days
Longmont, CO

Average sunshine days - Longmont, CO

The month with the most sunshine days is January (23.4 days).
The month with the least sunshine days is July (9.3 days).

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Average UV index
Longmont, CO

Average UV index - Longmont, CO

The months with the highest UV index are July and August (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 2).

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Average visibility
Longmont, CO

Average visibility - Longmont, CO

The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).

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Longmont, Colorado, USA

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