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May Weather in Alton, United States

Last updated: June 24, 2025

In May, the average temperature in Alton, United States is a brisk 13°C (56°F), but prepare for variability as it can drop as low as 0°C (33°F) or soar up to 32°C (90°F). Expect some moisture with an average precipitation amount of 74 mm (2.9 in) over about 10 days. Don’t forget to account for the average humidity of 72%, making it a month to dress comfortably!

May Temperature in Alton

In May, in Alton, the average temperature is 13°C (56°F). The maximum can reach 32°C (90°F), and the minimum can be as low as 0°C (33°F). It's a great time to pack for variable weather and enjoy outdoor activities while exploring Alton.

May Weather in Alton: Daily Temperature Highs, Lows, and Averages

The chart illustrates May temperature patterns in Alton, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Alton, May typically has an average temperature of 13°C (56°F), with highs reaching up to 32°C (90°F) and lows dropping to around 0°C (33°F).
JanFebMarAprMayJunJulAugSepOctNovDec242633445566727164523829
Data source: Temperature data for Alton 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 Alton

In Alton in May, the precipitation amount is 74 mm (2.9 in) spread over a period of 10 days.

May Precipitation Trends in Alton

The chart displays monthly precipitation patterns in Alton, 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 Alton, May typically receives around 74 mm (2.9 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec75847712874871347466119110119
Data source: Precipitation data for May generated using information from the Copernicus Climate Change Service.
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May Humidity in Alton

In Alton in May, humidity is 72%. With an average temperature of 13°C (56°F), this humidity feels like a damp blanket enveloping you, making outdoor activities somewhat uncomfortable and reminding travelers to stay hydrated and seek shade whenever possible.

May Average Humidity in Alton

This chart illustrates the average monthly humidity levels in Alton, 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 Alton is approximately 72%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec86%84%82%80%72%72%67%66%71%79%84%81%
Data source: Humidity data for May generated using information from the Copernicus Climate Change Service.

May UV Index in Alton

In Alton 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 Alton.

Maximum UV Index Levels in Alton for May

The chart shows the monthly maximum UV Index (UVI) for Alton 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 Alton typically reaches 9, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec3458910997532
Data source: Alton 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 Alton Compares to Other Months

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

This table compares monthly weather conditions in Alton, showing how May’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-5°C (24°F)75 mm (2.9 inches)86%moderate
February Weather-3°C (27°F)84 mm (3.3 inches)84%moderate
March Weather0°C (33°F)77 mm (3.0 inches)82%moderate
April Weather7°C (44°F)128 mm (5.0 inches)80%very high
May Weather13°C (56°F)74 mm (2.9 inches)72%very high
June Weather19°C (66°F)87 mm (3.4 inches)72%very high
July Weather22°C (72°F)134 mm (5.3 inches)67%very high
August Weather21°C (71°F)74 mm (2.9 inches)66%very high
September Weather18°C (64°F)66 mm (2.6 inches)71%high
October Weather11°C (52°F)119 mm (4.7 inches)78%moderate
November Weather3°C (39°F)110 mm (4.3 inches)84%moderate
December Weather-2°C (29°F)119 mm (4.7 inches)81%low

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