Last updated: June 24, 2025
In September, the average temperature in New Haven, United States hovers around 21°C (71°F). Prepare for a range, as temperatures can dip to a chilly 6°C (43°F) or soar to a sweltering 37°C (99°F). With 106 mm (4.2 in) of precipitation spread over 9 days, don’t forget your umbrella! Expect an average humidity of 73%, making for a pleasantly warm atmosphere.
In September in New Haven, the average temperature is 21°C (71°F). Maximum temperatures can reach up to 37°C (99°F), while the minimum can dip as low as 6°C (43°F). This range makes New Haven an ideal destination for travelers seeking both warm days and cooler evenings.
In New Haven in September, the total precipitation amount is 106 mm (4.2 in), spread over the course of 9 days.
In New Haven in September humidity is 73%. With an average temperature of 21°C (71°F), this humidity feels like a warm, enveloping blanket that can make outdoor activities a bit uncomfortable, but with proper hydration and breaks in the shade, it’s still manageable for traveling.
In New Haven in September, the maximum UV index is 8, which corresponds to a very high Exposure Category. This means that the time to burn is only 15 minutes. For more detailed information, you can refer to the Hourly UV Index in New Haven.
UV Risk Categories
Weather in New Haven varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in New Haven, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | 2°C (35°F) | 91 mm (3.6 inches) | 88% | moderate |
| February Weather | 4°C (39°F) | 131 mm (5.1 inches) | 88% | moderate |
| March Weather | 8°C (46°F) | 109 mm (4.3 inches) | 88% | high |
| April Weather | 13°C (55°F) | 138 mm (5.4 inches) | 86% | very high |
| May Weather | 19°C (66°F) | 141 mm (5.5 inches) | 82% | very high |
| June Weather | 23°C (73°F) | 152 mm (6.0 inches) | 84% | very high |
| July Weather | 25°C (78°F) | 111 mm (4.4 inches) | 82% | very high |
| August Weather | 24°C (75°F) | 123 mm (4.8 inches) | 73% | very high |
| September Weather | 21°C (71°F) | 106 mm (4.2 inches) | 73% | very high |
| October Weather | 15°C (60°F) | 108 mm (4.3 inches) | 81% | high |
| November Weather | 7°C (45°F) | 80 mm (3.2 inches) | 89% | moderate |
| December Weather | 4°C (40°F) | 119 mm (4.7 inches) | 86% | moderate |