August weather forecast
St. Louis, MO

A beautiful twilight over the Gateway Arch in St. Louis, Missouri
A beautiful twilight over the Gateway Arch in St. Louis, Missouri

Weather in August

The last month of the summer, August, is another hot month in St. Louis, with temperature in the range of an average low of 69.4°F (20.8°C) and an average high of 88°F (31.1°C).

Temperature

In St. Louis, the average high-temperature in August is almost the same as in July - a still hot 88°F (31.1°C). In St. Louis, in August, the average low-temperature is 69.4°F (20.8°C).

Heat index

In August, the average heat index is evaluated at a torrid 100.2°F (37.9°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 'real feel', 'feels like', 'apparent temperature', or 'felt air temperature', is a measure of how hot it feels when the actual air humidity is factored in. Additional factors like activity, clothing, metabolic differences, and pregnancy affect individual temperature impact. Bear in mind that direct sunshine exposure increases weather impact, and may raise 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. Under high air temperature and humidity (high heat index) conditions, perspiration is limited, and the perception of heat is increased. If the body can not disperse the excessive heat and body temperature reaches conditions of hyperthermia, above 99.5°F (37.5°C) to 100.9°F (38.3°C), thermal conditions are potentially life-threatening.

Humidity

In August, the average relative humidity in St. Louis is 70%.

Rainfall

In St. Louis, it is raining for 8.2 days, with typically 2.99" (75.9mm) of accumulated precipitation. In St. Louis, during the entire year, the rain falls for 112.6 days and collects up to 40.96" (1040.3mm) of precipitation.

Snowfall

May through October are months without snowfall in St. Louis, Missouri.

Daylight

In August, the average length of the day in St. Louis is 13h and 37min.
On the first day of the month, sunrise is at 6:02 am and sunset at 8:11 pm. On the last day of August, in St. Louis, sunrise is at 6:29 am and sunset at 7:32 pm CDT.

Sunshine

The average sunshine in August in St. Louis, Missouri, is 8.7h.

UV index

June through August, with an average maximum UV index of 9, are months with the highest UV index in St. Louis, Missouri. A UV Index estimate of 8 to 10 represents a very high health hazard from unsafe exposure to UV radiation for the ordinary person.
Note: The average daily UV index of 9 in August transform into the following instructions:
Take extra precautions. Protection against sun damage is required. 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. On bright days sunglasses that block both UVA and UVB rays should be worn. A hat with a wide brim is extremely helpful, as it can prevent roughly 50% of UV radiation from reaching the eyes. A broad-spectrum sunscreen of SPF 30+ should be liberally applied and re-applied every two hours, and immediately after an outdoor workout or a swim.
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FAQ

What is the temperature in August in St. Louis?

The average high-temperature, in August, in St. Louis, is 88°F (31.1°C), while the average low-temperature is 69.4°F (20.8°C). In August, the average heat index (a.k.a. 'apparent temperature', 'felt air temperature'), which factors the actual air temperature with the relative humidity, is evaluated at 100.2°F (37.9°C).

What is the average humidity in August in St. Louis?

In August, the average relative humidity is 70%.

How much does it rain in St. Louis in August?

In August, in St. Louis, Missouri, the rain falls for 8.2 days. Throughout August, 2.99" (75.9mm) of precipitation is accumulated.

When it does not snow in St. Louis?

May through October are months without snowfall in St. Louis, Missouri.

What is the average length of the day in August in St. Louis?

The average day length in August is 13h and 37min.

When are sunrise and sunset in August in St. Louis?

On the first day of August in St. Louis, sunrise is at 6:02 am and sunset at 8:11 pm. On the last day of the month, sunrise is at 6:29 am and sunset at 7:32 pm CDT.

How many hours of sunshine does St. Louis have in August?

The average sunshine duration in August in St. Louis is 8.7h.

What is the month with the highest UV index in St. Louis?

The months with the highest UV index in St. Louis, Missouri, are June through August, with an average maximum UV index of 9.

How high is the UV index in August in St. Louis?

In St. Louis, the average daily maximum UV index in August is 9. A UV Index of 8 to 10 symbolizes a very high health vulnerability from unsafe exposure to Sun's UV rays.
Average humidity
Average rainfall days
Average snowfall
Average snowfall days
Average sunshine
Average UV index

Average temperature in August
St. Louis, MO

Average temperature in August - St. Louis, MO
  • Average high temperature in August: 87.9°F

The warmest month (with the highest average high temperature) is July (89.1°F).
The month with the lowest average high temperature is January (39.9°F).

  • Average low temperature in August: 69.4°F

The month with the highest average low temperature is July (71°F).
The coldest month (with the lowest average low temperature) is January (23.7°F).

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Average humidity in August
St. Louis, MO

Average humidity in August - St. Louis, MO
  • Average humidity in August: 70%

The month with the highest relative humidity is December (75.8%).
The month with the lowest relative humidity is April (63.5%).

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Average rainfall in August
St. Louis, MO

Average rainfall in August - St. Louis, MO
  • Average rainfall in August: 3"

The wettest month (with the highest rainfall) is May (4.7").
The driest month (with the least rainfall) is February (2.2").

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Average rainfall days in August
St. Louis, MO

Average rainfall days in August - St. Louis, MO
  • Average rainfall days in August: 8.2 days

The month with the highest number of rainy days is May (11.9 days).
The month with the least rainy days is September (7.4 days).

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Average snowfall in August
St. Louis, MO

Average snowfall in August - St. Louis, MO
  • Average snowfall in August: 0"

The month with the highest snowfall is January (5.6").
The months with the least snowfall are May, June, July, August, September and October (0").

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Average snowfall days in August
St. Louis, MO

Average snowfall days in August - St. Louis, MO
  • Average snowfall days in August: 0 days

The month with the highest number of snowfall days is January (4.7 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
St. Louis, MO

Average daylight in August / Average sunshine in August - St. Louis, MO
  • Average daylight in August: 13h and 37min

The month with the longest days is June (Average daylight: 14h and 49min).
The month with the shortest days is December (Average daylight: 9h and 31min).

  • Average sunshine in August: 8h and 42min

The month with the most sunshine is July (Average sunshine: 10h and 0min).
The month with the least sunshine is December (Average sunshine: 4h and 12min).

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Average UV index in August
St. Louis, MO

Average UV index in August - St. Louis, MO
  • Average UV index in August: 9

The months with the highest UV index are June, July and August (UV index 9).
The months with the lowest UV index are January and December (UV index 2).

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