Allegheny County (Pittsburgh)
September
Weather in Allegheny County for September 2025
Your guide to Allegheny County weather in September - trends and predictions
In general, the average temperature in Allegheny County at the beginning of September is 28.7 °F. As the month progressed, temperatures tended to significantly cool down, reaching an average of 22.4 °F by the end of September.
Allegheny County sees moderate rainfall in September, averaging 9 rainy days.
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21
Dry days
9
Rainy days
0
Snow days
25°/13°
Temperatures
11 km/h
Avg max wind
70 %
Avg humidity
Allegheny County in September average weather
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| Mon. | Tue. | Wed. | Thu. | Fri. | Sat. | Sun. |
|---|---|---|---|---|---|---|
| 1  28° | 2  26° | 3  29° | 4  30° | 5  31° | 6 32° | 7  25° |
| 8 24° | 9 26° | 10 28° | 11 29° | 12 28° | 13 25° | 14 25° |
| 15 26° | 16 24° | 17 20° | 18  22° | 19 23° | 20  27° | 21 28° |
| 22 27° | 23 22° | 24  21° | 25 24° | 26 23° | 27 24° | 28 21° |
| 29 24° | 30 20° |
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Temperatures trend during September in Allegheny County
See the weather trend as well as the moving average line
September weather day by day
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| Date | Weather | Temperatures | Rain | UV | More |
|---|---|---|---|---|---|
| Sept. 1 | Sunny | 28° /14° | 0 mm | 7 | |
| Sept. 2 | Mist | 26° /11° | 0 mm | 7 | |
| Sept. 3 | Overcast | 29° /13° | 0 mm | 7 | |
| Sept. 4 | Thundery outbreaks possible | 30° /15° | 0 mm | 7 | |
| Sept. 5 | Partly cloudy | 31° /16° | 0 mm | 8 | |
| Sept. 6 | Thundery outbreaks possible | 32° /16° | 0.2 mm | 8 | |
| Sept. 7 | Light rain shower | 25° /14° | 6 mm | 6 | |
| Sept. 8 | Overcast | 24° /11° | 0 mm | 6 | |
| Sept. 9 | Mist | 26° /12° | 1.2 mm | 6 | |
| Sept. 10 | Light rain shower | 28° /13° | 7.9 mm | 7 | |
| Sept. 11 | Mist | 29° /14° | 0 mm | 7 | |
| Sept. 12 | Mist | 28° /15° | 0 mm | 7 | |
| Sept. 13 | Fog | 25° /13° | 2.8 mm | 6 | |
| Sept. 14 | Mist | 25° /12° | 0 mm | 6 | |
| Sept. 15 | Sunny | 26° /11° | 0 mm | 7 | |
| Sept. 16 | Overcast | 24° /10° | 0 mm | 5 | |
| Sept. 17 | Overcast | 20° /13° | 7.3 mm | 5 | |
| Sept. 18 | Patchy light rain with thunder | 22° /12° | 0.4 mm | 5 | |
| Sept. 19 | Overcast | 23° /14° | 0 mm | 5 | |
| Sept. 20 | Cloudy | 27° /12° | 0 mm | 6 | |
| Sept. 21 | Partly cloudy | 28° /17° | 5.4 mm | 7 | |
| Sept. 22 | Partly cloudy | 27° /15° | 0 mm | 7 | |
| Sept. 23 | Overcast | 22° /14° | 9.5 mm | 5 | |
| Sept. 24 | Light drizzle | 21° /15° | 12.4 mm | 5 | |
| Sept. 25 | Patchy rain possible | 24° /15° | 5.1 mm | 6 | |
| Sept. 26 | Overcast | 23° /14° | 1.5 mm | 6 | |
| Sept. 27 | Overcast | 24° /16° | 3.8 mm | 6 | |
| Sept. 28 | Light rain shower | 21° /14° | 4.5 mm | 5 | |
| Sept. 29 | Light rain shower | 24° /16° | 1.4 mm | 5 | |
| Sept. 30 | Mist | 20° /13° | 24.3 mm | 5 | |
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Important Notice
Our weather forecast for Allegheny County in September is based on the analysis of historical data rather than real-time forecast models. While this provides a general overview, weather conditions can change. We recommend that you check the Allegheny County forecast closer to your planned date for the most up-to-date weather information.
Allegheny County in September - FAQ
What are the expected maximum and minimum temperatures in Allegheny County during September?
Enjoy moderate daytime temperatures of up to 25° and cooler nights around 13°. Ideal for a range of outdoor activities, from hiking to city tours.
How much rainfall should be expected in Allegheny County during September?
In September, Allegheny County can expect light to moderate rainfall, totaling 38.5 mm across approximately 9 days. Occasional showers are possible, and planning ahead for them could be helpful.
What are the typical wind conditions in Allegheny County during September?
The average wind speed in Allegheny County during September is 11 km/h, suggesting breezy to windy conditions, depending on your activities.
September rainfall patterns in Allegheny County
Explore the daily rainfall trends and prepare for Allegheny Countys September weather 💧
UV exposure in Allegheny County during September
Stay informed about UV levels for safe outdoor activities throughout the month of September ☀️
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Where is Allegheny County?Get accurate weather forecasts for Allegheny County, located at latitude 40.441 and longitude -79.996. Stay updated with localized weather information tailored for Allegheny County.
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