Weather in Mercer County, New Jersey for September 2025
Rip Current Statement - See hour by hour.
Until now, September 2025 in Mercer County has been nearly identical to the historical average, with a temperature of 24.4 °F (showing only a slight deviation of -0.5 °F).
Expect cooler weather in the next days in Mercer County with the forecast suggesting a temperature of 22.5 °F, lower than the historical average.
In general, the average temperature in Mercer County at the beginning of September is 25 °F. As the month progressed, temperatures tended to significantly cool down, reaching an average of 20 °F by the end of September.
Mercer County experiences moderate rainfall in September, with an average of 10 rainy days and a total precipitation of 80.2 mm.
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Mercer County Weather September
Temperatures trend during September in Mercer County
September weather in Mercer County day by day
| Date | Weather | Temperatures | Rain | UV | More |
|---|---|---|---|---|---|
| Sept. 1 |  Light rain shower | 25° /17° | 1.6 mm | 6 | |
| Sept. 2 |  Partly cloudy | 26° /14° | 0 mm | 7 | |
| Sept. 3 |  Sunny | 24° /12° | 0 mm | 6 | |
| Sept. 4 | Partly cloudy | 26° /13° | 0 mm | 6 | |
| Sept. 5 | Sunny | 27° /16° | 17.5 mm | 6 | |
| Sept. 6 | Patchy rain possible | 27° /18° | 20.2 mm | 6 | |
| Sept. 7 | Light rain shower | 20° /13° | 43.9 mm | 5 | |
| Sept. 8 | Sunny | 22° /9° | 0 mm | 6 | |
| Sept. 9 | Sunny | 23° /11° | 0 mm | 6 | |
| Sept. 10 | Sunny | 23° /14° | 0 mm | 6 | |
| Sept. 11 | Partly cloudy | 25° /14° | 0 mm | 7 | |
| Sept. 12 | Sunny | 26° /14° | 0 mm | 7 | |
| Sept. 13 | Sunny | 26° /15° | 4.2 mm | 6 | |
| Sept. 14 | Sunny | 28° /16° | 0 mm | 7 | |
| Sept. 15 | Sunny | 27° /16° | 0 mm | 7 | |
| Sept. 16 | Patchy rain possible | 17° /14° | 0.1 mm | 1.2 | |
| Sept. 17 |  Overcast | 17° /15° | 0 mm | 0.4 | |
| Sept. 18 | Overcast | 28° /17° | 0 mm | 1.5 | |
| Sept. 19 | Sunny | 32° /18° | 0 mm | 0 | |
| Sept. 20 | Sunny | 22° /14° | 0 mm | 5 | |
| Sept. 21 | Sunny | 23° /13° | 0 mm | 5 | |
| Sept. 22 | Partly cloudy | 24° /14° | 0 mm | 5 | |
| Sept. 23 | Sunny | 26° /15° | 0 mm | 5 | |
| Sept. 24 | Patchy rain possible | 23° /17° | 4.4 mm | 4 | |
| Sept. 25 | Patchy rain possible | 24° /19° | 3.6 mm | 5 | |
| Sept. 26 | Patchy rain possible | 24° /18° | 3.1 mm | 5 | |
| Sept. 27 |  Heavy rain | 18° /16° | 23.7 mm | 4 | |
| Sept. 28 | Patchy rain possible | 15° /12° | 4 mm | 3 | |
| Sept. 29 |  Light rain | 17° /15° | 10 mm | 4 | |
| Sept. 30 | Overcast | 19° /15° | 0 mm | 4 | |
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Mercer County in September - FAQ
September rainfall patterns in Mercer County
UV exposure in Mercer County during September
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Where is Mercer County?Get accurate weather forecasts for Mercer County, located at latitude 40.349 and longitude -74.659. Stay updated with localized weather information tailored for Mercer County.