September weather forecast
Stillwater, OK

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Weather in September

In September, the oppressive heat of summer in Stillwater begins to lessen, marking the onset of autumn. The change in season is also marked by shorter days. Relative to August, the conditions in September are a bit cooler and less humid, but the weather remains largely warm. The average maximum temperature decreases to 84.4°F (29.1°C), as the heat of the summer begins to fade.

Temperature

The advent of September brings a slight shift in average high-temperature, moving from a tropical 92.3°F (33.5°C) in August to a moderately hot 84.4°F (29.1°C). In Stillwater, September nights witness a steady temperature drop to a refreshing 64.4°F (18°C).

Heat index

The heat index value for September is appraised at a tropical 89.6°F (32°C). Continuous exposure and activity could induce a sense of tiredness and subsequently, heat cramps.
Evaluating the heat index requires understanding its values in the shade and with gentle winds. Heat index values may rise by up to 15 Fahrenheit (8 Celsius) degrees when exposed to direct sunlight.
Note: The heat index, also known as 'real feel' or 'apparent temperature', is a calculated temperature value of how hot it feels when the moisture in the air is factored in. The effect of weather is individual, with a variety of people experiencing it differently due to distinctions in body mass, height, and level of activity. In direct sunlight, the heat's impact can be heightened, potentially leading to an increase in the heat index by 15 Fahrenheit (8 Celsius) degrees. Heat index values are largely significant for babies and toddlers. Children typically face more danger than adults as their sweat production is usually lower. Additionally, the bigger skin surface compared to their small size and the increased heat due to their activeness exacerbate the risk.

Humidity

In Stillwater, the average relative humidity in September is 67%.

Rainfall

In September, the rain falls for 12 days. Throughout September, 2.91" (74mm) of precipitation is accumulated. Throughout the year, in Stillwater, there are 121.4 rainfall days, and 25.28" (642mm) of precipitation is accumulated.

Snowfall

In Stillwater, snow does not fall in April through October.

Daylight

In September, the average length of the day is 12h and 23min.
On the first day of September, sunrise is at 7:00 am and sunset at 7:55 pm. On the last day of the month, sunrise is at 7:23 am and sunset at 7:12 pm CDT.

Sunshine

The average sunshine in September in Stillwater is 8.6h.

UV index

In September, the average daily maximum UV index is 5. A UV Index of 3 to 5 symbolizes a moderate health risk from unprotected exposure to Sun's UV rays for the ordinary person.
Note: The UV index of 5 during September leads to these advisories:
Exercise caution. The susceptibility of light skin individuals to burns is less than 30 minutes. Solar radiation peaks around mid-day, so it's wise to limit exposure to the Sun at this time. A wide-brim hat offers excellent sun protection for the eyes, ears, face, and neck. Sunglasses with UVA and UVB protection significantly reduce eye damage from sun exposure.
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Frequently asked questions

How hot is it in Stillwater in September?

In Stillwater, 84.4°F (29.1°C) is the average high-temperature and 64.4°F (18°C) is the average low-temperature during September. The average heat index (a.k.a. 'felt air temperature', 'feels like'), which combines relative humidity and air temperature, in September is appraised at 89.6°F (32°C).

What is the average humidity in September in Stillwater?

In Stillwater, Oklahoma, the average relative humidity in September is 67%.

How much does it rain in Stillwater in September?

In Stillwater, Oklahoma, in September, during 12 rainfall days, 2.91" (74mm) of precipitation is typically accumulated.

When it does not snow in Stillwater?

April through October are months without snowfall.

How many hours of daylight does Stillwater have in September?

The average day length in September is 12h and 23min.

What time are sunrise and sunset in September in Stillwater?

In September, on the first day of the month, sunrise is at 7:00 am and sunset at 7:55 pm. On the last day of the month, in Stillwater, Oklahoma, sunrise is at 7:23 am and sunset at 7:12 pm CDT.

How long on average sun shines in September in Stillwater?

The average sunshine duration in September is 8.6h.

How high is the UV index in September in Stillwater?

In Stillwater, the average daily maximum UV index in September is 5. A UV Index of 3 to 5 symbolizes a moderate vulnerability from unsafe exposure to Sun's UV rays.
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
Stillwater, OK

Average temperature in September - Stillwater, OK
  • Average high temperature in September: 84.4°F

The warmest month (with the highest average high temperature) is July (93°F).
The month with the lowest average high temperature is January (47.5°F).

  • Average low temperature in September: 64.4°F

The month with the highest average low temperature is July (73°F).
The coldest month (with the lowest average low temperature) is January (30.6°F).

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Average pressure in September
Stillwater, OK

Average pressure in September - Stillwater, OK
  • Average pressure in September: 29.98"Hg

The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is June (29.87"Hg).

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Average wind speed in September
Stillwater, OK

Average wind speed in September - Stillwater, OK
  • Average wind speed in September: 8.5mph

The windiest month (with the highest average wind speed) is April (11.5mph).
The calmest month (with the lowest average wind speed) is August (8.2mph).

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Average humidity in September
Stillwater, OK

Average humidity in September - Stillwater, OK
  • Average humidity in September: 67%

The month with the highest relative humidity is May (75%).
The month with the lowest relative humidity is August (62%).

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Average rainfall in September
Stillwater, OK

Average rainfall in September - Stillwater, OK
  • Average rainfall in September: 2.91"

The wettest month (with the highest rainfall) is May (4.25").
The driest month (with the least rainfall) is December (0.98").

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Average rainfall days in September
Stillwater, OK

Average rainfall days in September - Stillwater, OK
  • Average rainfall days in September: 12 days

The month with the highest number of rainy days is May (14.6 days).
The month with the least rainy days is January (4.8 days).

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Average snowfall in September
Stillwater, OK

Average snowfall in September - Stillwater, OK
  • Average snowfall in September: 0"

The month with the highest snowfall is February (1.42").
The months with the least snowfall are April, May, June, July, August, September and October (0").

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Average snowfall days in September
Stillwater, OK

Average snowfall days in September - Stillwater, OK
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is February (2.8 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).

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Average daylight in September /
Average sunshine in September
Stillwater, OK

Average daylight in September / Average sunshine in September - Stillwater, OK
  • Average daylight in September: 12h and 2min

The month with the longest days is June (Average daylight: 14h and 36min).
The month with the shortest days is December (Average daylight: 9h and 48min).

  • Average sunshine in September: 8h and 4min

The month with the most sunshine is August (Average sunshine: 11h and 12min).
The month with the least sunshine is December (Average sunshine: 6h and 6min).

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Average sunshine days in September
Stillwater, OK

Average sunshine days in September - Stillwater, OK
  • Average sunshine days in September: 15.8 days

The month with the most sunshine days is January (22.9 days).
The month with the least sunshine days is May (13.7 days).

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Average UV index in September
Stillwater, OK

Average UV index in September - Stillwater, OK
  • Average UV index in September: 5

The months with the highest UV index are June, July and August (UV index 7).
The month with the lowest UV index is December (UV index 2).

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Average cloud cover in September
Stillwater, OK

Average cloud cover in September - Stillwater, OK
  • Average cloud cover in September: 26

The month with the most cloud cover is March (Cloud cover 37).
The month with the least cloud cover is August (Cloud cover 19).

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Average visibility in September
Stillwater, OK

Average visibility in September - Stillwater, OK
  • 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).

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Stillwater, Oklahoma, USA

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