September weather forecastMerrillville, IN
September
Weather in September
September marks the start of fall in Merrillville with a gradual decrease in daylight hours from 13.8 in August to 12.5. The transition from summer to fall is subtle with average high temperatures decreasing to 73.9°F (23.3°C), making it a pleasant time to visit the city. The waning days of summer fuse with the emerging brisk fall climate, rendering a unique beauty to the locale. The season's change ushers in the time for fall festivities and the city's natural autumn landscape becomes a sight to behold.Temperature
September brings a slight decrease in temperature, down from 79.5°F (26.4°C) in August to a still moderately hot 73.9°F (23.3°C). Merrillville experiences a mean temperature of 57.7°F (14.3°C) during September nights.Humidity
In September, the average relative humidity is 76%.Rainfall
In Merrillville, during September, the rain falls for 12.7 days and regularly aggregates up to 1.85" (47mm) of precipitation. Throughout the year, there are 146.6 rainfall days, and 23.31" (592mm) of precipitation is accumulated.Snowfall
In Merrillville, Indiana, snow does not fall in May through September.Daylight
In September, the average length of the day is 12h and 28min.On the first day of the month, sunrise is at 6:16 am and sunset at 7:21 pm. On the last day of September, sunrise is at 6:45 am and sunset at 6:32 pm CDT.
Sunshine
In Merrillville, the average sunshine in September is 8.3h.UV index
The average daily maximum UV index in September is 4. A UV Index reading of 3 to 5 represents a medium health hazard from unprotected exposure to Sun's UV rays for the ordinary person.Note: The maximum daily UV index of 4 during September translates into the following directions:
Be cautious. Those with fair skin can be subjected to burns in fewer than 30 minutes. Direct exposure to the Sun's intense radiation around midday should be avoided for health reasons. For minimizing sun-related eye damage, always choose sunglasses with UVA and UVB coverage.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Merrillville, IN
- Average high temperature in September: 73.9°F
The warmest month (with the highest average high temperature) is July (81.5°F).
The month with the lowest average high temperature is January (30°F).
- Average low temperature in September: 57.7°F
The month with the highest average low temperature is July (65.5°F).
The coldest month (with the lowest average low temperature) is January (18.9°F).
Average pressure in September
Merrillville, IN
- Average pressure in September: 30.03"Hg
The month with the highest atmospheric pressure is January (30.11"Hg).
The month with the lowest atmospheric pressure is June (29.93"Hg).
Average wind speed in September
Merrillville, IN
- Average wind speed in September: 7.3mph
The windiest month (with the highest average wind speed) is January (10.3mph).
The calmest month (with the lowest average wind speed) is August (6.3mph).
Average humidity in September
Merrillville, IN
- Average humidity in September: 76%
The month with the highest relative humidity is February (83%).
The month with the lowest relative humidity is October (73%).
Average rainfall in September
Merrillville, IN
- Average rainfall in September: 1.85"
The wettest month (with the highest rainfall) is June (3.15").
The driest month (with the least rainfall) is November (1.06").
Average rainfall days in September
Merrillville, IN
- Average rainfall days in September: 12.7 days
The month with the highest number of rainy days is July (17.6 days).
The month with the least rainy days is February (5.3 days).
Average snowfall in September
Merrillville, IN
- Average snowfall in September: 0"
The month with the highest snowfall is February (3.5").
The months with the least snowfall are May, June, July, August and September (0").
Average snowfall days in September
Merrillville, IN
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (12.4 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
Merrillville, IN
- 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 12min).
- Average sunshine in September: 8h and 18min
The month with the most sunshine is August (Average sunshine: 9h and 48min).
The month with the least sunshine is January (Average sunshine: 3h and 30min).
Average sunshine days in September
Merrillville, IN
- Average sunshine days in September: 14.5 days
The month with the most sunshine days is November (17.4 days).
The month with the least sunshine days is July (10.2 days).
Average UV index in September
Merrillville, IN
- Average UV index in September: 4
The months with the highest UV index are June and July (UV index 6).
The months with the lowest UV index are January and December (UV index 1).
Average cloud cover in September
Merrillville, IN
- Average cloud cover in September: 35
The month with the most cloud cover is January (Cloud cover 64).
The month with the least cloud cover is August (Cloud cover 32).
Average visibility in September
Merrillville, IN
- Average visibility in September: 6mi
The months with the highest visibility are March, April, May, June, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February and July (5mi).
