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May Weather in Alton, United States

Last updated: June 24, 2025

In May, the average temperature in Alton, United States hovers around 19°C (67°F), with daily variations ranging from a cool 4°C (39°F) to a warm 34°C (94°F). Rainfall is a frequent visitor, accumulating to 150 mm (5.9 in) over 13 days, while the air maintains a high average humidity of 82%.

May Temperature in Alton

In May in Alton, the average temperature is 19°C (67°F). The maximum can reach 34°C (94°F), while the minimum can drop as low as 4°C (39°F). This range makes it a perfect time to explore outdoor activities, but be sure to pack for both warm and cool weather.

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 19°C (67°F), with highs reaching up to 34°C (94°F) and lows dropping to around 4°C (39°F).
JanFebMarAprMayJunJulAugSepOctNovDec313446546776797672584338
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 150 mm (5.9 in) spread over 13 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 150 mm (5.9 inches) of precipitation spread over approximately 13 days.
JanFebMarAprMayJunJulAugSepOctNovDec737813212315010196119671007054
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 82%. With an average temperature of 19°C (67°F), this humidity feels like a heavy blanket wrapping around you, making each step feel sluggish and the air thick as you explore the sights.

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 82%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec82%80%80%80%82%83%81%80%76%76%85%86%
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 reaches 10, which corresponds to a very high Exposure Category. With a time to burn of just 15 minutes, it's crucial to take precautions. For more 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 10, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec356910111199643
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 Weather0°C (32°F)73 mm (2.9 inches)82%moderate
February Weather1°C (35°F)78 mm (3.1 inches)80%moderate
March Weather8°C (46°F)132 mm (5.2 inches)80%high
April Weather12°C (55°F)123 mm (4.9 inches)80%very high
May Weather19°C (67°F)150 mm (5.9 inches)82%very high
June Weather25°C (77°F)101 mm (4.0 inches)83%extreme
July Weather26°C (79°F)96 mm (3.8 inches)81%extreme
August Weather24°C (76°F)119 mm (4.7 inches)80%very high
September Weather22°C (72°F)67 mm (2.6 inches)76%very high
October Weather15°C (59°F)100 mm (3.9 inches)76%high
November Weather6°C (44°F)70 mm (2.8 inches)85%moderate
December Weather3°C (38°F)54 mm (2.1 inches)86%moderate

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