Contents
- Weather in September
- Frequently asked questions
- Average temperature in September
- Average pressure in September
- Average wind speed in September
- Average humidity in September
- Average rainfall in September
- Average rainfall days in September
- Average snowfall in September
- Average snowfall days in September
- Average daylight in September
- Average sunshine in September
- Average sunshine days in September
- Average UV index in September
- Average cloud cover in September
- Average visibility in September
Weather in September
Temperature
The advent of September brings a slight shift in average high-temperature, moving from a moderately hot 81.1°F (27.3°C) in August to a still warm 75.6°F (24.2°C). Mercer experiences a mean temperature of 56.1°F (13.4°C) during September nights.Humidity
In Mercer, the average relative humidity in September is 76%.Rainfall
In Mercer, during September, the rain falls for 10.4 days and regularly aggregates up to 1.5" (38mm) of precipitation. Throughout the year, there are 115.1 rainfall days, and 19.21" (488mm) of precipitation is accumulated.Snowfall
May through September are months without snowfall.Daylight
In Mercer, the average length of the day in September is 12h and 27min.On the first day of the month, sunrise is at 6:46 am and sunset at 7:50 pm. On the last day of September, in Mercer, Iowa, sunrise is at 7:14 am and sunset at 7:01 pm CDT.
Sunshine
In Mercer, the average sunshine in September is 9.2h.UV index
The average daily maximum UV index in September is 5. A UV Index estimate of 3 to 5 represents a moderate health risk from exposure to the Sun's UV radiation for average individuals.Note: In September, a regular UV index of 5 translates into these guidelines:
Be cautious. Those with fair skin can be subjected to burns in fewer than 30 minutes. Midday is the peak time for the Sun's radiation; stay in the shade and protect yourself. Sunglasses providing both UVA and UVB protection are non-negotiable on sunlit days.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What are the temperatures in September?
What is the average humidity in September?
How many days does it rain in September?
When it does not snow in Mercer?
Does it snow in September?
How many hours of daylight does Mercer have in September?
What time are sunrise and sunset in September in Mercer?
How many hours of sunshine does Mercer have in September?
What is the UV index intensity in September?
Average temperature in September
Mercer, IA
- Average high temperature in September: 75.6°F
The warmest month (with the highest average high temperature) is July (83.3°F).
The month with the lowest average high temperature is January (29.3°F).
- Average low temperature in September: 56.1°F
The month with the highest average low temperature is July (65.8°F).
The coldest month (with the lowest average low temperature) is January (16°F).
Average pressure in September
Mercer, IA
- Average pressure in September: 30.01"Hg
The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is June (29.88"Hg).
Average wind speed in September
Mercer, IA
- Average wind speed in September: 8.2mph
The windiest months (with the highest average wind speed) are March and April (10.5mph).
The calmest month (with the lowest average wind speed) is July (7mph).
Average humidity in September
Mercer, IA
- Average humidity in September: 76%
The months with the highest relative humidity are January and June (81%).
The month with the lowest relative humidity is October (70%).
Average rainfall in September
Mercer, IA
- Average rainfall in September: 1.5"
The wettest month (with the highest rainfall) is June (3.74").
The driest month (with the least rainfall) is February (0.51").
Average rainfall days in September
Mercer, IA
- Average rainfall days in September: 10.4 days
The month with the highest number of rainy days is May (16.5 days).
The month with the least rainy days is February (3 days).
Average snowfall in September
Mercer, IA
- Average snowfall in September: 0"
The month with the highest snowfall is January (2.28").
The months with the least snowfall are May, June, July, August and September (0").
Average snowfall days in September
Mercer, IA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (8.4 days).
The months with the least snowfall days are June, July, August and September (0 days).
Average daylight in September /
Average sunshine in September
Mercer, IA
- Average daylight in September: 12h and 3min
The month with the longest days is June (Average daylight: 15h and 6min).
The month with the shortest days is December (Average daylight: 9h and 18min).
- Average sunshine in September: 9h and 1min
The month with the most sunshine is July (Average sunshine: 10h and 18min).
The month with the least sunshine is January (Average sunshine: 4h and 24min).
Average sunshine days in September
Mercer, IA
- Average sunshine days in September: 17.5 days
The month with the most sunshine days is November (22.5 days).
The month with the least sunshine days is May (12 days).
Average UV index in September
Mercer, IA
- Average UV index in September: 5
The months with the highest UV index are June, July and August (UV index 6).
The month with the lowest UV index is January (UV index 1).
Average cloud cover in September
Mercer, IA
- Average cloud cover in September: 29
The month with the most cloud cover is January (Cloud cover 52).
The months with the least cloud cover are July and September (Cloud cover 29).
Average visibility in September
Mercer, IA
- Average visibility in September: 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).
Mercer, Iowa, USA
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