September Weather in Rosslyn, United States

Last updated: June 24, 2025

In Rosslyn, United States, the average temperature in September settles at a pleasant 22°C (72°F). However, don't be surprised by the extremes—temperatures can dip to a cool 5°C (42°F) or soar up to a sweltering 36°C (97°F). Expect an average of 95 mm (3.8 in) of precipitation over 11 days, accompanied by a noteworthy average humidity of 75%.

September Temperature in Rosslyn

In September in Rosslyn, the average temperature is 22°C (72°F), with maximums reaching 36°C (97°F) and minimums dipping as low as 5°C (42°F). This range makes it a perfect time for travelers to enjoy comfortable outdoor activities while being prepared for warm days and cooler nights.

September Weather in Rosslyn: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Rosslyn, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Rosslyn, September typically has an average temperature of 22°C (72°F), with highs reaching up to 36°C (97°F) and lows dropping to around 5°C (42°F).

Data source: Temperature data for Rosslyn generated using information from the Copernicus Climate Change Service.

September Precipitation in Rosslyn

In Rosslyn in September, the precipitation amount is 95 mm (3.8 in) spread over 11 days.

September Precipitation Trends in Rosslyn

The chart displays monthly precipitation patterns in Rosslyn, with values for each month alongside September’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how September’s conditions compare to those of other months. In Rosslyn, September typically receives around 95 mm (3.8 inches) of precipitation spread over approximately 11 days.

Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.

Choose your preferred precipitation unit

Millimeters (mm) Inches (in)

September Humidity in Rosslyn

In Rosslyn in September, humidity is 75%. With an average temperature of 22°C (72°F), this humidity feels like a warm embrace, making outdoor activities enjoyable yet requiring travelers to stay hydrated and take breaks in shaded areas.

September Average Humidity in Rosslyn

This chart illustrates the average monthly humidity levels in Rosslyn, with September’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In September, average humidity in Rosslyn is approximately 75%, offering insight into how humid the weather typically is during this month.

Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Rosslyn

In Rosslyn 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 Rosslyn.

Maximum UV Index Levels in Rosslyn for September

The chart shows the monthly maximum UV Index (UVI) for Rosslyn in September, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In September, the maximum UV index in Rosslyn typically reaches 8, which falls under the very high exposure category.

Data source: Rosslyn September UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

Extreme (11+): Avoid the sun, stay in shade.
Very High (8-10): Limit sun exposure.
High (6-7): Use SPF 30+ and protective clothing.
Moderate (3-5): Midday shade recommended.
Low (0-2): No protection needed.

How September Weather in Rosslyn Compares to Other Months

Weather in Rosslyn varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Rosslyn, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Rosslyn, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	3°C (37°F)	61 mm (2.4 inches)	84%	moderate
February Weather	5°C (41°F)	98 mm (3.9 inches)	83%	moderate
March Weather	8°C (46°F)	87 mm (3.4 inches)	83%	high
April Weather	14°C (57°F)	100 mm (4.0 inches)	81%	very high
May Weather	19°C (66°F)	127 mm (5.0 inches)	78%	very high
June Weather	24°C (75°F)	118 mm (4.7 inches)	79%	very high
July Weather	27°C (81°F)	157 mm (6.2 inches)	74%	very high
August Weather	25°C (77°F)	140 mm (5.5 inches)	72%	very high
September Weather	22°C (72°F)	95 mm (3.8 inches)	75%	very high
October Weather	17°C (62°F)	104 mm (4.1 inches)	81%	high
November Weather	8°C (47°F)	81 mm (3.2 inches)	85%	moderate
December Weather	5°C (41°F)	93 mm (3.7 inches)	84%	moderate