Climate and monthly weather forecast
O'Fallon, MO

Weather in January

January, the same as December, is a wintry winter month in O'Fallon, Missouri, with temperature in the range of an average high of 37.4°F (3°C) and an average low of 23.7°F (-4.6°C). With an average high-temperature of 37.4°F (3°C) and an average low-temperature of 23.7°F (-4.6°C), January is the coldest month. Weather in January »

Weather in February

February, the last month of the winter in O'Fallon, is also a wintry month, with temperature in the range of an average high of 41.9°F (5.5°C) and an average low of 27°F (-2.8°C). In February, the average high-temperature is practically the same as in January - a still cold 41.9°F (5.5°C). Weather in February »

Weather in March

The first month of the spring, March, is a fresh month in O'Fallon, Missouri, with an average temperature varying between 37.9°F (3.3°C) and 54.1°F (12.3°C). In March, the average high-temperature rises from a cold 41.9°F (5.5°C) in February to a fresh 54.1°F (12.3°C). Weather in March »

Weather in April

April in O'Fallon, Missouri, is a comfortable spring month, with an average temperature varying between 47.3°F (8.5°C) and 65.3°F (18.5°C). In O'Fallon, Missouri, the average high-temperature in April rises from a fresh 54.1°F (12.3°C) in March to a comfortable 65.3°F (18.5°C). Weather in April »

Weather in May

The last month of the spring, May, is a moderately hot month in O'Fallon, Missouri, with temperature in the range of an average low of 57°F (13.9°C) and an average high of 74.5°F (23.6°C). In May, the average high-temperature rises from an enjoyable 65.3°F (18.5°C) in April to a moderately hot 74.5°F (23.6°C). Weather in May »

Weather in June

June, the first month of the summer in O'Fallon, is still a warm month, with an average temperature fluctuating between 66.2°F (19°C) and 83.8°F (28.8°C). In O'Fallon, Missouri, the average high-temperature in June rises from a moderately hot 74.5°F (23.6°C) in May to a still warm 83.8°F (28.8°C). Weather in June »

Weather in July

July in O'Fallon, Missouri, is a tropical summer month, with an average temperature varying between 87.1°F (30.6°C) and 68.5°F (20.3°C). The warmest month is July, with an average high-temperature of 87.1°F (30.6°C) and an average low-temperature of 68.5°F (20.3°C). In July, the average heat index is estimated at a very hot 101.5°F (38.6°C). Weather in July »

Weather in August

The last month of the summer, August, is also a moderately hot month in O'Fallon, Missouri, with temperature in the range of an average high of 85.5°F (29.7°C) and an average low of 66.6°F (19.2°C). In August, the average high-temperature is practically the same as in July - a warm 85.5°F (29.7°C). Weather in August »

Weather in September

September, the first month of the autumn in O'Fallon, is also a moderately hot month, with an average temperature varying between 60.1°F (15.6°C) and 79.5°F (26.4°C). In September, the average high-temperature marginally drops from 85.5°F (29.7°C) in August to a still warm 79.5°F (26.4°C). Weather in September »

Weather in October

October, like September, in O'Fallon, Missouri, is another comfortable autumn month, with an average temperature ranging between max 66.2°F (19°C) and min 48.7°F (9.3°C). In O'Fallon, Missouri, the average high-temperature in October drops from a moderately hot 79.5°F (26.4°C) in September to an enjoyable 66.2°F (19°C). Weather in October »

Weather in November

The last month of the autumn, November, is also a fresh month in O'Fallon, Missouri, with an average temperature ranging between max 53.2°F (11.8°C) and min 37.6°F (3.1°C). In O'Fallon, Missouri, the average high-temperature in November drops from a comfortable 66.2°F (19°C) in October to a cool 53.2°F (11.8°C). Weather in November »

Weather in December

The first month of the winter, December, is still a cold month in O'Fallon, Missouri, with an average temperature ranging between max 41.9°F (5.5°C) and min 30.4°F (-0.9°C). In O'Fallon, the average high-temperature in December decreases from a fresh 53.2°F (11.8°C) in November to a cold 41.9°F (5.5°C). Weather in December »
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FAQ

What is the coldest month in O'Fallon?

The coldest month is January, with an average high-temperature of 37.4°F (3°C) and an average low-temperature of 23.7°F (-4.6°C).

How much does it rain in O'Fallon?

Throughout the year, there are 132.3 rainfall days, and 21.06" (535mm) of precipitation is accumulated.

When does it snow in O'Fallon?

January through March, November and December are months with snowfall in O'Fallon, Missouri.

How many days does it snow in O'Fallon?

Throughout the year, in O'Fallon, there are 19 snowfall days, and 4.13" (105mm) of snow is accumulated.

What is the month with the least sunshine in O'Fallon?

January and February, with an average of 4.7h of sunshine, are months with the least sunshine in O'Fallon, Missouri.

When is the lowest UV index in O'Fallon?

The months with the lowest UV index in O'Fallon, Missouri, are January, February, November and December, with an average maximum UV index of 2.

When does it snow the most in O'Fallon?

The month with the most snowfall in O'Fallon is February, when snow falls for 5.8 days and typically aggregates up to 1.61" (41mm) of snow.

When is Daylight Saving Time (DST) in O'Fallon?

On Sunday, March 13. 2022, at 2:00 am, Daylight Saving Time starts, and the time zone changes from CST to CDT. Daylight Saving Time ends Sunday, November 6. 2022, at 2:00 am, and the time zone reverts from CDT to CST.

When it does not snow in O'Fallon?

In O'Fallon, Missouri, snow does not fall in April through October.

What is the most humid month in O'Fallon?

May is the most humid month in O'Fallon, Missouri, with an average relative humidity of 79%.

What is the wettest month in O'Fallon?

May is the month with the most rainfall. Rain falls for 15.7 days and accumulates 2.76" (70mm) of precipitation.

What is the month with the highest UV index in O'Fallon?

May through August, with an average maximum UV index of 6, are months with the highest UV index.

When are the longest days in O'Fallon?

The month with the longest days in O'Fallon is June, with an average of 14h and 50min of daylight.

What month has the most sunshine in O'Fallon?

With an average of 10.5h of sunshine, June has the most sunshine of the year in O'Fallon, Missouri.

What is the warmest month in O'Fallon?

With an average high-temperature of 87.1°F (30.6°C) and an average low-temperature of 68.5°F (20.3°C), July is the warmest month.

What is the least humid month in O'Fallon?

The least humid month in O'Fallon is October, with an average relative humidity of 70%.

What is the driest month in O'Fallon?

The month with the least rainfall in O'Fallon, Missouri, is December, when the rain falls for 7 days and typically collects 0.91" (23mm) of precipitation.

What is the month with the shortest days in O'Fallon?

The month with the shortest days is December, with an average of 9h and 30min of daylight.

Average temperature
O'Fallon, MO

Average temperature - O

The warmest month (with the highest average high temperature) is July (87.1°F).
The month with the lowest average high temperature is January (37.4°F).

The month with the highest average low temperature is July (68.5°F).
The coldest month (with the lowest average low temperature) is January (23.7°F).

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Average pressure
O'Fallon, MO

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The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is June (29.92"Hg).

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Average wind speed
O'Fallon, MO

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The windiest month (with the highest average wind speed) is January (9.1mph).
The calmest month (with the lowest average wind speed) is July (5.5mph).

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Average rainfall
O'Fallon, MO

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The wettest month (with the highest rainfall) is May (2.76").
The driest month (with the least rainfall) is December (0.91").

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Average rainfall days
O'Fallon, MO

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The month with the highest number of rainy days is May (15.7 days).
The month with the least rainy days is February (6.8 days).

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Average snowfall
O'Fallon, MO

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The month with the highest snowfall is February (1.61").
The months with the least snowfall are April, May, June, July, August, September and October (0").

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Average snowfall days
O'Fallon, MO

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The months with the highest number of snowfall days are January and February (5.8 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).

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Average daylight / Average sunshine
O'Fallon, MO

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The month with the longest days is June (Average daylight: 14h and 50min).
The month with the shortest days is December (Average daylight: 9h and 30min).

The month with the most sunshine is June (Average sunshine: 10h and 30min).
The months with the least sunshine are January and February (Average sunshine: 4h and 42min).

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Average sunshine days
O'Fallon, MO

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The month with the most sunshine days is December (20.6 days).
The month with the least sunshine days is July (12.6 days).

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Average UV index
O'Fallon, MO

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The months with the highest UV index are May, June, 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
O'Fallon, MO

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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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