September weather forecastPrinceton, NJ
September
Weather in September
With a further decline in temperatures, September starts to blend summer's residue with the touch of incoming fall. The onset of autumn, in Princeton, is characterized by mild temperatures coupled with a sprinkling of rain. The daylight duration contracts, and the sky radiates less sunshine, rendering a russet tone to the surroundings. It marks the transition from the warmth of August to the cooler tones of October. September, differing from August, presents reduced temperatures, shortened daylight hours, and less sunshine.Temperature
With the arrival of September, Princeton notices a mild change in the average high-temperature, sliding from August's 82.9°F (28.3°C) to a still moderately hot 75.7°F (24.3°C). In September, Princeton encounters an average low-temperature of 59°F (15°C) during the night.Humidity
The average relative humidity in September is 77%.Rainfall
The month with the least rainfall is September, when the rain falls for 10 days and typically collects 0.67" (17mm) of precipitation.Snowfall
June through October are months without snowfall.Daylight
In Princeton, the average length of the day in September is 12h and 27min.On the first day of the month, sunrise is at 6:26 am and sunset at 7:30 pm. On the last day of September, sunrise is at 6:54 am and sunset at 6:42 pm EDT.
Sunshine
The average sunshine in September is 8.8h.UV index
In September, the average daily maximum UV index in Princeton is 4. A UV Index value of 3 to 5 symbolizes a moderate health risk from unsafe exposure to UV radiation for the average person.Note: A maximum high daily UV index of 4 during September translates into the following directions:
Be vigilant - Suggestions to stave off sun damage are provided. The Sun is at its harshest during midday; protect yourself by staying in shaded areas and minimizing exposure. Opt for tightly woven and loose clothing to enhance protection from the Sun.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Princeton, NJ
- Average high temperature in September: 75.7°F
The warmest month (with the highest average high temperature) is July (84.7°F).
The month with the lowest average high temperature is January (36.9°F).
- Average low temperature in September: 59°F
The month with the highest average low temperature is July (66.9°F).
The coldest month (with the lowest average low temperature) is January (24.3°F).
Average pressure in September
Princeton, NJ
- Average pressure in September: 30.05"Hg
The month with the highest atmospheric pressure is November (30.11"Hg).
The month with the lowest atmospheric pressure is June (29.93"Hg).
Average wind speed in September
Princeton, NJ
- Average wind speed in September: 6mph
The windiest month (with the highest average wind speed) is March (8.8mph).
The calmest month (with the lowest average wind speed) is August (5.4mph).
Average humidity in September
Princeton, NJ
- Average humidity in September: 77%
The month with the highest relative humidity is October (79%).
The month with the lowest relative humidity is April (73%).
Average rainfall in September
Princeton, NJ
- Average rainfall in September: 0.67"
The wettest month (with the highest rainfall) is July (1.69").
The driest month (with the least rainfall) is September (0.67").
Average rainfall days in September
Princeton, NJ
- Average rainfall days in September: 10 days
The month with the highest number of rainy days is July (13.9 days).
The month with the least rainy days is January (6.1 days).
Average snowfall in September
Princeton, NJ
- Average snowfall in September: 0"
The month with the highest snowfall is March (1.42").
The months with the least snowfall are June, July, August, September and October (0").
Average snowfall days in September
Princeton, NJ
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (4.6 days).
The months with the least snowfall days are June, July, August, September and October (0 days).
Average daylight in September /
Average sunshine in September
Princeton, NJ
- Average daylight in September: 12h and 24min
The month with the longest days is June (Average daylight: 15h and 0min).
The month with the shortest days is December (Average daylight: 9h and 24min).
- Average sunshine in September: 8h and 48min
The month with the most sunshine is July (Average sunshine: 10h and 30min).
The month with the least sunshine is February (Average sunshine: 4h and 48min).
Average sunshine days in September
Princeton, NJ
- Average sunshine days in September: 17.2 days
The month with the most sunshine days is January (21.8 days).
The month with the least sunshine days is July (13.3 days).
Average UV index in September
Princeton, NJ
- Average UV index in September: 4
The months with the highest UV index are June, July and August (UV index 6).
The months with the lowest UV index are January, February, March, November and December (UV index 2).
Average cloud cover in September
Princeton, NJ
- Average cloud cover in September: 38
The months with the most cloud cover are February, March and December (Cloud cover 47).
The months with the least cloud cover are July and August (Cloud cover 33).
Average visibility in September
Princeton, NJ
- Average visibility in September: 6mi
The months with the highest visibility are January, February, March, April, June, July, August, September, October, November and December (6mi).
The month with the lowest visibility is May (5mi).
