September weather forecastSt. Louis, MO
September
Weather in September
September is a transitional month, marking the beginning of fall in St. Louis, Missouri. As the month progresses, daily temperatures gradually drop, providing relief from the summer heat. The average temperature lowers to a comfortable 60.6°F (15.9°C). Despite the descent of temperature, daylight hours remain relatively long, ensuring residents ample time to enjoy the colourful changes in the local flora. The occurrence of rainfall lessens, culminating in an often dry end to the month.Temperature
St. Louis's progression into September involves a gentle drop in the average high-temperature, from a hot 88°F (31.1°C) in August to a moderately hot 80.2°F (26.8°C). St. Louis encounters a steady low-temperature average of 60.6°F (15.9°C) throughout the month of September.Humidity
The average relative humidity in September in St. Louis is 71.6%.Rainfall
In September, in St. Louis, the rain falls for 7.4 days. Throughout September, 3.15" (80mm) of precipitation is accumulated. In St. Louis, during the entire year, the rain falls for 112.6 days and collects up to 40.94" (1040mm) of precipitation.Snowfall
May through October are months without snowfall in St. Louis.Daylight
In September, the average length of the day in St. Louis is 12h and 25min.On the first day of the month, sunrise is at 6:30 am and sunset at 7:30 pm. On the last day of September, in St. Louis, sunrise is at 6:56 am and sunset at 6:44 pm CDT.
Sunshine
In St. Louis, Missouri, the average sunshine in September is 7.9h.UV index
The average daily maximum UV index in September in St. Louis is 7. A UV Index estimate of 6 to 7 represents a high health hazard from unsafe exposure to UV radiation for the average person.Note: A typical high UV index of 7 in September suggests the following recommendations:
Undertake protective measures and comply with sun safety rules. Shielding against skin and eye damage is essential. Limit direct sun exposure and seek shade between 10 a.m. and 4 p.m., the time of the most intense UV radiation, noting that shade structures may not provide total sun protection. It's wise to wear UVA and UVB-blocking sunglasses when the sun shines brightly.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
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).
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%).
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").
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).
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").
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).
Average daylight in September /
Average sunshine in September
St. Louis, MO
- Average daylight in September: 12h and 24min
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: 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).
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).
