September 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 September

The first month of the autumn, September, is also a moderately hot month in St. Louis, with an average temperature ranging between max 80.2°F (26.8°C) and min 60.6°F (15.9°C).

Temperature

In September, the average high-temperature in St. Louis marginally drops from a tropical 88°F (31.1°C) in August to a warm 80.2°F (26.8°C). In September, in St. Louis, the average low-temperature is 60.6°F (15.9°C).

Humidity

In September, the average relative humidity in St. Louis, Missouri, is 71.6%.

Rainfall

In St. Louis, during 7.4 rainfall days, 3.13" (79.5mm) of precipitation is typically accumulated. Throughout the year, in St. Louis, there are 112.6 rainfall days, and 40.96" (1040.3mm) of precipitation is accumulated.

Snowfall

In St. Louis, snow does not fall in May through October.

Daylight

In St. Louis, the average length of the day in September is 12h and 25min.
On the first day of the month, sunrise is at 6:30 am and sunset at 7:31 pm. On the last day of September, in St. Louis, sunrise is at 6:55 am and sunset at 6:45 pm CDT.

Sunshine

In St. Louis, Missouri, the average sunshine in September is 7.9h.

UV index

In September, the average daily maximum UV index in St. Louis is 7. A UV Index value of 6 to 7 symbolizes a high health hazard from unsafe exposure to UV radiation for the ordinary person.
Note: The average daily UV index of 7 in September transform into the following instructions:
Take precautions and utilize sun safety practices. Protection against skin and eye damage is required. The Sun's UV radiation is most powerful between 10 a.m. and 4 p.m. To the extent possible, limit exposure to the direct sun during these hours. 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 average humidity in September in St. Louis?

The average relative humidity in September in St. Louis, Missouri, is 71.6%.

How many days does it rain in September in St. Louis?

In St. Louis, during September, the rain falls for 7.4 days and regularly aggregates up to 3.13" (79.5mm) of precipitation.

When it does not snow in St. Louis?

May through October are months without snowfall.

How many hours of daylight does St. Louis have in September?

In St. Louis, Missouri, the average day length in September is 12h and 25min.

What time are sunrise and sunset in September in St. Louis?

In September, on the first day of the month, sunrise is at 6:30 am and sunset at 7:31 pm. On the last day of the month, in St. Louis, Missouri, sunrise is at 6:55 am and sunset at 6:45 pm CDT.

How long on average sun shines in September in St. Louis?

In St. Louis, the average sunshine duration in September is 7.9h.

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

In St. Louis, Missouri, the average daily maximum UV index in September is 7. A UV Index of 6 to 7 symbolizes a high health threat from exposure to Sun's UV rays.
Average humidity
Average rainfall days
Average snowfall
Average snowfall days
Average sunshine
Average UV index

Average temperature in September
St. Louis, MO

Average temperature in September - St. Louis, MO
  • Average high temperature in September: 80.2°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 September: 60.6°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 September
St. Louis, MO

Average humidity in September - St. Louis, MO
  • Average humidity in September: 71.6%

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 September
St. Louis, MO

Average rainfall in September - St. Louis, MO
  • Average rainfall in September: 3.1"

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 September
St. Louis, MO

Average rainfall days in September - St. Louis, MO
  • Average rainfall days in September: 7.4 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 September
St. Louis, MO

Average snowfall in September - St. Louis, MO
  • Average snowfall in September: 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 September
St. Louis, MO

Average snowfall days in September - St. Louis, MO
  • Average snowfall days in September: 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 September /
Average sunshine in September
St. Louis, MO

Average daylight in September / Average sunshine in September - St. Louis, MO
  • Average daylight in September: 12h and 25min

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 September: 7h and 54min

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 September
St. Louis, MO

Average UV index in September - St. Louis, MO
  • Average UV index in September: 7

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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