August weather forecast
O'Fallon, MO

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).

Temperature

In August, the average high-temperature is practically the same as in July - a warm 85.5°F (29.7°C). In August, the average low-temperature is 66.6°F (19.2°C).

Heat index

The average heat index in August is estimated at a sweltering 95.9°F (35.5°C). Take special precautions - heat exhaustion and heat cramps are expected. Heatstroke may occur with lengthy activity.
Note that heat index values are valued for light wind and location in the shade. Exposure to direct sunshine can increase heat index values by up to 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'feels like', 'real feel', 'felt air temperature', or 'apparent temperature', is calculated by taking the relative humidity value for a specific location and factoring it into the air temperature reading. Additional factors like clothing, wind, pregnancy, and activity influence one's weather impression. Be aware that direct exposure to sunlight increases heat impact and may raise the heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are especially crucial for babies and toddlers. Young children are generally more endangered than adults, as they usually less sweat. And also, due to larger skin surface relative to their small bodies and higher heat production as a result of their activity.
To prevent overheating and help regulate its internal temperature, the human body sweat and rely on the evaporation to cool down. A higher relative humidity affects normal body cooling by reducing the evaporation rate, subsequently lowering the rate at which the body cools and increasing the perception of heat. When heat gain surpasses the level the body can shed, body temperature begins to increase, and consequently, overheating and dehydration can occur, with varying severity.

Humidity

The average relative humidity in August is 75%.

Rainfall

In August, the rain falls for 12.8 days. Throughout August, 2.48" (63mm) of precipitation is accumulated. In O'Fallon, during the entire year, the rain falls for 132.3 days and collects up to 21.06" (535mm) of precipitation.

Snowfall

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

Daylight

In O'Fallon, Missouri, the average length of the day in August is 13h and 38min.
On the first day of the month, sunrise is at 6:04 am and sunset at 8:14 pm. On the last day of August, sunrise is at 6:31 am and sunset at 7:34 pm CDT.

Sunshine

In O'Fallon, the average sunshine in August is 10.2h.

UV index

The months with the highest UV index in O'Fallon are May through August, with an average maximum UV index of 6. A UV Index reading of 6 to 7 represents a high health risk from unsafe exposure to UV radiation for the ordinary person.
Note: The average daily UV index of 6 in August transform into the following instructions:
Take precautions and adopt sun safety practices. Protection against sunburn is obliged. Seek shade and minimize exposure to direct Sun in a period between 10 a.m. and 4 p.m. when UV radiation is most intense; keep in mind that shade structures like parasols or canopies do not provide perfect sun protection. Sun-protective clothing, a long-sleeved shirt and pants, a wide-brimmed hat, and UVA and UVB-blocking sunglasses are particularly helpful in blocking UV radiation's harmful effects.
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FAQ

What is the temperature in August in O'Fallon?

In August, in O'Fallon, Missouri, the average high-temperature is 85.5°F (29.7°C), and the average low-temperature is 66.6°F (19.2°C). In August, the average heat index (a.k.a. 'apparent temperature', 'felt air temperature'), which combines air temperature and relative humidity, is estimated at 95.9°F (35.5°C).

What is the average humidity in August in O'Fallon?

The average relative humidity in August is 75%.

How many days does it rain in August in O'Fallon?

In O'Fallon, in August, during 12.8 rainfall days, 2.48" (63mm) of precipitation is typically accumulated.

When it does not snow in O'Fallon?

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

What is the average length of the day in August in O'Fallon?

In August, the average day length is 13h and 38min.

What time are sunrise and sunset in August in O'Fallon?

On the first day of August in O'Fallon, sunrise is at 6:04 am and sunset at 8:14 pm. On the last day of the month, sunrise is at 6:31 am and sunset at 7:34 pm CDT.

How long on average sun shines in August in O'Fallon?

In August, the average sunshine duration in O'Fallon, Missouri, is 10.2h.

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.

What is the UV index reading in August in O'Fallon?

In August, the average daily maximum UV index in O'Fallon is 6. A UV Index reading of 6 to 7 represents a high health risk from exposure to the Sun's UV radiation.
Average humidity
Average rainfall days
Average snowfall
Average snowfall days
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in August
O'Fallon, MO

Average temperature in August - O
  • Average high temperature in August: 85.5°F

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).

  • Average low temperature in August: 66.6°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 in August
O'Fallon, MO

Average pressure in August - O
  • Average pressure in August: 29.97"Hg

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 in August
O'Fallon, MO

Average wind speed in August - O
  • Average wind speed in August: 5.6mph

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 humidity in August
O'Fallon, MO

Average humidity in August - O
  • Average humidity in August: 75%

The month with the highest relative humidity is May (79%).
The month with the lowest relative humidity is October (70%).

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Average rainfall in August
O'Fallon, MO

Average rainfall in August - O
  • Average rainfall in August: 2.48"

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 in August
O'Fallon, MO

Average rainfall days in August - O
  • Average rainfall days in August: 12.8 days

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 in August
O'Fallon, MO

Average snowfall in August - O
  • Average snowfall in August: 0"

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 in August
O'Fallon, MO

Average snowfall days in August - O
  • Average snowfall days in August: 0 days

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 in August /
Average sunshine in August
O'Fallon, MO

Average daylight in August / Average sunshine in August - O
  • Average daylight in August: 13h and 38min

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).

  • Average sunshine in August: 10h and 12min

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 in August
O'Fallon, MO

Average sunshine days in August - O
  • Average sunshine days in August: 14.7 days

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 in August
O'Fallon, MO

Average UV index in August - O
  • Average UV index in August: 6

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 cloud cover in August
O'Fallon, MO

Average cloud cover in August - O
  • Average cloud cover in August: 28

The month with the most cloud cover is January (Cloud cover 50).
The months with the least cloud cover are June, July, August and September (Cloud cover 28).

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Average visibility in August
O'Fallon, MO

Average visibility in August - O
  • Average visibility in August: 6mi

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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