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May Weather in St. Charles, United States

Last updated: June 24, 2025

In St. Charles, United States, the average temperature in May is a comfortable 16°C (61°F). However, be prepared for a wide range of temperatures, as it can drop to a chilly -2°C (28°F) or soar to a hot 35°C (95°F). This month also sees 168 mm (6.6 in) of precipitation spread over 15 days, contributing to an average humidity level of 79%. Stay hydrated and enjoy the diverse weather!

May Temperature in St. Charles

In May in St. Charles, the average temperature is 16°C (61°F), with maximums reaching 35°C (95°F) and minimums dropping as low as -2°C (28°F). Travelers should be prepared for a wide range of temperatures and pack accordingly to enjoy their visit.

May Weather in St. Charles: Daily Temperature Highs, Lows, and Averages

The chart illustrates May temperature patterns in St. Charles, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In St. Charles, May typically has an average temperature of 16°C (61°F), with highs reaching up to 35°C (95°F) and lows dropping to around -2°C (28°F).
JanFebMarAprMayJunJulAugSepOctNovDec242739486071757267543832
Data source: Temperature data for St. Charles 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.

May Precipitation in St. Charles

In St. Charles in May, the total precipitation amount is 168 mm (6.6 in) collected over a period of 15 days.

May Precipitation Trends in St. Charles

The chart displays monthly precipitation patterns in St. Charles, with values for each month alongside May’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how May’s conditions compare to those of other months. In St. Charles, May typically receives around 168 mm (6.6 inches) of precipitation spread over approximately 15 days.
JanFebMarAprMayJunJulAugSepOctNovDec61598111716914010699911275453
Data source: Precipitation data for May generated using information from the Copernicus Climate Change Service.
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May Humidity in St. Charles

In St. Charles in May humidity is 79%. With an average temperature of 16°C (61°F), this humidity feels like a warm, moist embrace, making travel a bit more challenging as the air tends to weigh heavily, but it also offers a refreshing atmosphere perfect for exploring local sights and enjoying nature.

May Average Humidity in St. Charles

This chart illustrates the average monthly humidity levels in St. Charles, with May’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In May, average humidity in St. Charles is approximately 79%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec82%83%84%85%79%82%80%81%80%82%88%84%
Data source: Humidity data for May generated using information from the Copernicus Climate Change Service.

May UV Index in St. Charles

In St. Charles in May, the maximum UV index is 9, which corresponds to a very high Exposure Category. The time to burn is just 15 minutes, so it's essential to take precautions. For detailed information, you can check the Hourly UV Index in St. Charles.

Maximum UV Index Levels in St. Charles for May

The chart shows the monthly maximum UV Index (UVI) for St. Charles in May, 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 May, the maximum UV index in St. Charles typically reaches 9, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec34689101098632
Data source: St. Charles May 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 May Weather in St. Charles Compares to Other Months

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

This table compares monthly weather conditions in St. Charles, showing how May’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-4°C (25°F)61 mm (2.4 inches)82%moderate
February Weather-3°C (27°F)59 mm (2.3 inches)83%moderate
March Weather4°C (39°F)81 mm (3.2 inches)84%high
April Weather9°C (48°F)117 mm (4.6 inches)85%very high
May Weather16°C (61°F)168 mm (6.6 inches)79%very high
June Weather22°C (72°F)140 mm (5.5 inches)82%very high
July Weather24°C (75°F)106 mm (4.2 inches)80%very high
August Weather22°C (73°F)99 mm (3.9 inches)81%very high
September Weather19°C (67°F)91 mm (3.6 inches)80%very high
October Weather12°C (54°F)127 mm (5.0 inches)82%high
November Weather3°C (38°F)54 mm (2.1 inches)88%moderate
December Weather0°C (32°F)53 mm (2.1 inches)84%low

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