September weather forecast
Saint Clair, MO

Share

Weather in September

The first month of the autumn, September, is also a moderately hot month in Saint Clair, Missouri, with temperature in the range of an average high of 80.2°F (26.8°C) and an average low of 59.2°F (15.1°C).

Temperature

September's arrival coincides with a soft drop in the average high-temperature, subtly decreasing from August's tropical 87.3°F (30.7°C) to a moderately hot 80.2°F (26.8°C). Throughout September, Saint Clair experiences a low-temperature average of 59.2°F (15.1°C).

Humidity

The average relative humidity in September is 74%.

Rainfall

In Saint Clair, during September, the rain falls for 9.8 days and regularly aggregates up to 1.46" (37mm) of precipitation. Throughout the year, there are 126.7 rainfall days, and 20.63" (524mm) of precipitation is accumulated.

Snowfall

April through October are months without snowfall.

Daylight

In September, the average length of the day is 12h and 25min.
On the first day of the month, sunrise is at 6:34 am and sunset at 7:33 pm. On the last day of September, in Saint Clair, sunrise is at 6:59 am and sunset at 6:47 pm CDT.

Sunshine

In September, the average sunshine is 9.4h.

UV index

In September, the average daily maximum UV index is 5. A UV Index of 3 to 5 symbolizes a moderate threat to health from unprotected exposure to Sun's UV rays for the ordinary person.
Note: The UV index of 5 during September leads to these advisories:
Prioritize safety - Suggestions to prevent sun damage are offered. Sun exposure should be minimized, especially during midday, to avoid harmful UV radiation. Employ a hat with a wide brim for robust protection, cutting UV exposure by half. Mind you! Snow reflection can increase the intensity of the Sun's UV radiation nearly twofold.
Updated: Jul 10, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

What is the temperature in September in Saint Clair?

The average high-temperature, in September, in Saint Clair, is 80.2°F (26.8°C), while the average low-temperature is 59.2°F (15.1°C). The average heat index (a.k.a. 'apparent temperature', 'felt air temperature'), which factors the actual air temperature with the relative humidity, in August is calculated to be 100.4°F (38°C).

What is the average humidity in September?

The average relative humidity in September is 74%.

How many days does it rain in September?

In September, the rain falls for 9.8 days. Throughout September, 1.46" (37mm) of precipitation is accumulated.

When it does not snow?

In Saint Clair, snow does not fall in April through October.

What is the average length of the day in September?

In September, the average day length is 12h and 25min.

When is the sunrise / sunset in September?

On the first day of September, sunrise is at 6:34 am and sunset at 7:33 pm. On the last day of the month, sunrise is at 6:59 am and sunset at 6:47 pm CDT.

How many hours of sunshine does Saint Clair have in September?

The average sunshine duration in September is 9.4h.

What is the UV index intensity in September in Saint Clair?

In Saint Clair, the average daily maximum UV index in September is 5. A UV Index of 3 to 5 symbolizes a moderate health threat from exposure to the Sun's UV radiation.
Average humidity
Average rainfall days
Average snowfall
Average snowfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in September
Saint Clair, MO

Average temperature in September - Saint Clair, MO
  • Average high temperature in September: 80.2°F

The warmest month (with the highest average high temperature) is July (88.9°F).
The month with the lowest average high temperature is January (39°F).

  • Average low temperature in September: 59.2°F

The month with the highest average low temperature is July (68°F).
The coldest month (with the lowest average low temperature) is January (24.3°F).

Average pressure in September
Saint Clair, MO

Average pressure in September - Saint Clair, MO
  • Average pressure in September: 30.02"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).

Average wind speed in September
Saint Clair, MO

Average wind speed in September - Saint Clair, MO
  • Average wind speed in September: 5.7mph

The windiest month (with the highest average wind speed) is January (8.5mph).
The calmest months (with the lowest average wind speed) are July and August (5.3mph).

Average humidity in September
Saint Clair, MO

Average humidity in September - Saint Clair, MO
  • Average humidity in September: 74%

The month with the highest relative humidity is May (78%).
The month with the lowest relative humidity is October (72%).

Average rainfall in September
Saint Clair, MO

Average rainfall in September - Saint Clair, MO
  • Average rainfall in September: 1.46"

The wettest months (with the highest rainfall) are April and May (2.48").
The driest months (with the least rainfall) are January and February (0.98").

Average rainfall days in September
Saint Clair, MO

Average rainfall days in September - Saint Clair, MO
  • Average rainfall days in September: 9.8 days

The month with the highest number of rainy days is May (15.4 days).
The month with the least rainy days is January (5.9 days).

Average snowfall in September
Saint Clair, MO

Average snowfall in September - Saint Clair, MO
  • Average snowfall in September: 0"

The month with the highest snowfall is February (1.57").
The months with the least snowfall are April, May, June, July, August, September and October (0").

Average snowfall days in September
Saint Clair, MO

Average snowfall days in September - Saint Clair, MO
  • Average snowfall days in September: 0.1 days

The month with the highest number of snowfall days is January (6.2 days).
The months with the least snowfall days are May, June, July and August (0 days).

Average daylight in September /
Average sunshine in September
Saint Clair, MO

Average daylight in September / Average sunshine in September - Saint Clair, MO
  • Average daylight in September: 12h and 2min

The month with the longest days is June (Average daylight: 14h and 48min).
The month with the shortest days is December (Average daylight: 9h and 30min).

  • Average sunshine in September: 9h and 2min

The months with the most sunshine are June and July (Average sunshine: 10h and 24min).
The months with the least sunshine are January and February (Average sunshine: 4h and 42min).

Average sunshine days in September
Saint Clair, MO

Average sunshine days in September - Saint Clair, MO
  • Average sunshine days in September: 18.1 days

The month with the most sunshine days is January (20.6 days).
The month with the least sunshine days is May (13.7 days).

Average UV index in September
Saint Clair, MO

Average UV index in September - Saint Clair, MO
  • Average UV index in September: 5

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).

Average cloud cover in September
Saint Clair, MO

Average cloud cover in September - Saint Clair, MO
  • Average cloud cover in September: 31

The months with the most cloud cover are January and February (Cloud cover 49).
The months with the least cloud cover are June and July (Cloud cover 29).

Average visibility in September
Saint Clair, MO

Average visibility in September - Saint Clair, MO
  • Average visibility in September: 5mi

The months with the highest visibility are January, February, March, April, June, July, October, November and December (6mi).
The months with the lowest visibility are May, August and September (5mi).

Saint Clair, Missouri, USA

Weather forecast for your location

1. Click Locate me button
2. Allow the app to use your location