Last updated: June 24, 2025
In September, the average temperature in Greenwich, United States is a pleasant 18°C (64°F). However, be prepared for a range of temperatures, as it can dip to a chilly 0°C (33°F) and soar up to a warm 33°C (91°F). Rain is a possibility too, with an average precipitation of 87 mm (3.4 in) spread over about 8 days. Don't forget to account for the average humidity level of 72%, which can make it feel a bit warmer!
In September in Greenwich, the average temperature is 18°C (64°F), with maximums reaching 33°C (91°F) and minimums dropping as low as 0°C (33°F). This wide temperature range makes it essential for travelers to pack layers to ensure comfort throughout their stay.
In Greenwich in September, the precipitation amount is 87 mm (3.4 in), which occurs over a span of 8 days.
In Greenwich in September, humidity is 72%. With an average temperature of 18°C (64°F), this humidity feels like a warm, sticky embrace, making travel somewhat uncomfortable as the air clings to your skin, leaving you longing for a refreshing breeze.
In Greenwich in September, the maximum UV index is 7, which corresponds to the high Exposure Category. This means that the time to burn is approximately 25 minutes. For more detailed information, you can check the Hourly UV Index in Greenwich.
UV Risk Categories
Weather in Greenwich varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Greenwich, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | -3°C (26°F) | 77 mm (3.0 inches) | 89% | moderate |
| February Weather | -2°C (29°F) | 95 mm (3.8 inches) | 88% | moderate |
| March Weather | 2°C (35°F) | 79 mm (3.1 inches) | 86% | high |
| April Weather | 8°C (47°F) | 121 mm (4.8 inches) | 84% | very high |
| May Weather | 15°C (59°F) | 89 mm (3.5 inches) | 76% | very high |
| June Weather | 20°C (68°F) | 82 mm (3.2 inches) | 72% | very high |
| July Weather | 23°C (73°F) | 108 mm (4.3 inches) | 66% | very high |
| August Weather | 22°C (72°F) | 80 mm (3.2 inches) | 64% | very high |
| September Weather | 18°C (64°F) | 87 mm (3.4 inches) | 72% | high |
| October Weather | 12°C (53°F) | 142 mm (5.6 inches) | 81% | moderate |
| November Weather | 4°C (39°F) | 106 mm (4.2 inches) | 87% | moderate |
| December Weather | -1°C (31°F) | 99 mm (3.9 inches) | 84% | low |