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September Weather in St. Mary's, United States

Last updated: June 24, 2025

In September, the average temperature in St. Mary's, United States hovers around 8°C (47°F). While you might experience a minimum chill of -3°C (28°F), the warmth can peak at a pleasant 18°C (65°F). Expect 91 mm (3.6 in) of precipitation spread over about 14 days, leading to an average humidity of 92%. Prepare for a moody, yet captivating season!

September Temperature in St. Mary's

In September in St. Mary's, the average temperature is 8°C (47°F). The maximum can reach 18°C (65°F) and the minimum can be as low as -3°C (28°F). Be prepared for a range of temperatures, making it a great time for layering and enjoying both cool and mild weather while exploring.

September Weather in St. Mary's: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in St. Mary's, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In St. Mary's, September typically has an average temperature of 8°C (47°F), with highs reaching up to 18°C (65°F) and lows dropping to around -3°C (28°F).
JanFebMarAprMayJunJulAugSepOctNovDec71217304555565446362013
Data source: Temperature data for St. Mary's generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in St. Mary's

In St. Mary's in September, the precipitation amount is 91 mm (3.6 in) over a span of 14 days.

September Precipitation Trends in St. Mary's

The chart displays monthly precipitation patterns in St. Mary's, 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 St. Mary's, September typically receives around 91 mm (3.6 inches) of precipitation spread over approximately 14 days.
JanFebMarAprMayJunJulAugSepOctNovDec316554476455638691785559
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in St. Mary's

In St. Mary's in September humidity is 92%. With an average temperature of 8°C (47°F), this humidity feels like a heavy blanket enveloping you, making outdoor activities uncomfortable and exhausting for travelers.

September Average Humidity in St. Mary's

This chart illustrates the average monthly humidity levels in St. Mary's, 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 St. Mary's is approximately 92%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec98%96%85%78%80%86%89%91%92%90%93%98%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in St. Mary's

In St. Mary's in September, the maximum UV index is 3, which corresponds to a moderate Exposure Category. The time to burn is approximately 30 minutes. For more details on the hourly UV index in St. Mary's, you can check the information here.

Maximum UV Index Levels in St. Mary's for September

The chart shows the monthly maximum UV Index (UVI) for St. Mary's 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 St. Mary's typically reaches 3, which falls under the moderate exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec113456653211
Data source: St. Mary's 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 St. Mary's Compares to Other Months

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

This table compares monthly weather conditions in St. Mary's, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-14°C (7°F)30 mm (1.2 inches)98%low
February Weather-11°C (12°F)65 mm (2.6 inches)96%low
March Weather-8°C (17°F)54 mm (2.1 inches)85%moderate
April Weather-1°C (30°F)47 mm (1.8 inches)78%moderate
May Weather7°C (45°F)63 mm (2.5 inches)80%moderate
June Weather13°C (55°F)55 mm (2.2 inches)86%high
July Weather14°C (57°F)63 mm (2.5 inches)89%high
August Weather12°C (54°F)86 mm (3.4 inches)91%moderate
September Weather8°C (47°F)91 mm (3.6 inches)92%moderate
October Weather2°C (36°F)78 mm (3.1 inches)90%low
November Weather-7°C (20°F)55 mm (2.2 inches)93%low
December Weather-11°C (13°F)59 mm (2.3 inches)98%low

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