September weather forecastMerrimac, IA
September
Weather in September
September, the first month of the autumn in Merrimac, is still a warm month, with an average temperature varying between 56.7°F (13.7°C) and 76.3°F (24.6°C).Temperature
The onset of September results in a small decrease in the average high-temperature, moderately receding from a warm 81.7°F (27.6°C) in August to a still moderately hot 76.3°F (24.6°C). Merrimac, in September, experiences an average temperature of 56.7°F (13.7°C) at night.Humidity
In September, the average relative humidity is 75%.Rainfall
In Merrimac, in September, during 11.5 rainfall days, 2.56" (65mm) of precipitation is typically accumulated. Throughout the year, there are 140.1 rainfall days, and 29.92" (760mm) of precipitation is accumulated.Snowfall
May through September are months without snowfall.Daylight
The average length of the day in September is 12h and 27min.On the first day of the month, sunrise is at 6:34 am and sunset at 7:39 pm. On the last day of September, sunrise is at 7:03 am and sunset at 6:49 pm CDT.
Sunshine
In Merrimac, the average sunshine in September is 9.3h.UV index
In Merrimac, the average daily maximum UV index in September is 4. A UV Index value of 3 to 5 symbolizes a medium vulnerability from unprotected exposure to Sun's UV rays for ordinary individuals.Note: The daily high UV index of 4 during September translates into the following recommendations:
Guard yourself - Avoiding sunburn is suggested. UV radiation from the Sun is most dangerous during midday; take precautions and seek shade. Shield yourself from the harmful effects of UV radiation with sun-protective attire, a hat, and quality sunglasses.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Merrimac, IA
- Average high temperature in September: 76.3°F
The warmest month (with the highest average high temperature) is July (82.4°F).
The month with the lowest average high temperature is January (29.7°F).
- Average low temperature in September: 56.7°F
The month with the highest average low temperature is July (65.3°F).
The coldest month (with the lowest average low temperature) is January (17.4°F).
Average pressure in September
Merrimac, IA
- Average pressure in September: 30.02"Hg
The month with the highest atmospheric pressure is January (30.15"Hg).
The month with the lowest atmospheric pressure is June (29.9"Hg).
Average wind speed in September
Merrimac, IA
- Average wind speed in September: 7.9mph
The windiest month (with the highest average wind speed) is January (10.7mph).
The calmest months (with the lowest average wind speed) are July and August (6.9mph).
Average humidity in September
Merrimac, IA
- Average humidity in September: 75%
The month with the highest relative humidity is July (83%).
The month with the lowest relative humidity is October (71%).
Average rainfall in September
Merrimac, IA
- Average rainfall in September: 2.56"
The wettest month (with the highest rainfall) is May (4.29").
The driest months (with the least rainfall) are February and December (1.38").
Average rainfall days in September
Merrimac, IA
- Average rainfall days in September: 11.5 days
The month with the highest number of rainy days is May (18.3 days).
The month with the least rainy days is February (4.6 days).
Average snowfall in September
Merrimac, IA
- Average snowfall in September: 0"
The month with the highest snowfall is January (4.76").
The months with the least snowfall are May, June, July, August and September (0").
Average snowfall days in September
Merrimac, IA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (9.6 days).
The months with the least snowfall days are May, June, July, August and September (0 days).
Average daylight in September /
Average sunshine in September
Merrimac, IA
- Average daylight in September: 12h and 30min
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 18min
The month with the most sunshine is July (Average sunshine: 10h and 0min).
The month with the least sunshine is January (Average sunshine: 4h and 0min).
Average sunshine days in September
Merrimac, IA
- Average sunshine days in September: 16.5 days
The month with the most sunshine days is October (18.4 days).
The month with the least sunshine days is May (10.6 days).
Average UV index in September
Merrimac, IA
- Average UV index in September: 4
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
Merrimac, IA
- Average cloud cover in September: 31
The month with the most cloud cover is January (Cloud cover 56).
The months with the least cloud cover are July, August and September (Cloud cover 31).
Average visibility in September
Merrimac, IA
- Average visibility in September: 6mi
The months with the highest visibility are January, February, March, April, May, June, August, September, October, November and December (6mi).
The month with the lowest visibility is July (5mi).
