May Weather in Alton, United States

Last updated: June 24, 2025

In May, the average temperature in Alton, United States is a comfortable 19°C (67°F). However, temperatures can range from a chilly 3°C (37°F) to a warm 33°C (91°F). Expect 181 mm (7.1 in) of precipitation spread over 15 days, and prepare for high humidity levels averaging 83%.

May Temperature in Alton

In May in Alton, the average temperature is 19°C (67°F), with maximums reaching up to 33°C (91°F) and minimums dipping as low as 3°C (37°F). This comfortable climate makes it an ideal time for travelers to explore the diverse attractions that Alton has to offer.

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 33°C (91°F) and lows dropping to around 3°C (37°F).

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

May Precipitation in Alton

In Alton in May, the precipitation amount is 181 mm (7.1 in) spread over 15 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 181 mm (7.1 inches) of precipitation spread over approximately 15 days.

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

Choose your preferred precipitation unit

Millimeters (mm) Inches (in)

May Humidity in Alton

In Alton in May humidity is 83%. With an average temperature of 19°C (67°F), this humidity feels like a warm, tropical blanket wrapping around you, making traveling feel a bit sluggish and sticky, yet still inviting as long as you stay hydrated and take breaks in the shade.

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 83%, offering insight into how humid the weather typically is during this month.

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 11, which corresponds to an extreme Exposure Category. With a time to burn of just 10 minutes, it's essential to take precautions. For more details, 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 11, which falls under the extreme exposure category.

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.
	Temperature	Precipitation	Humidity	UV
January Weather	2°C (36°F)	85 mm (3.3 inches)	83%	moderate
February Weather	4°C (40°F)	111 mm (4.4 inches)	81%	high
March Weather	10°C (50°F)	148 mm (5.8 inches)	80%	high
April Weather	13°C (56°F)	164 mm (6.5 inches)	80%	very high
May Weather	19°C (67°F)	181 mm (7.1 inches)	83%	extreme
June Weather	24°C (76°F)	85 mm (3.3 inches)	83%	extreme
July Weather	26°C (80°F)	80 mm (3.2 inches)	76%	extreme
August Weather	25°C (77°F)	106 mm (4.2 inches)	69%	very high
September Weather	23°C (73°F)	62 mm (2.4 inches)	68%	very high
October Weather	16°C (60°F)	121 mm (4.8 inches)	72%	high
November Weather	8°C (47°F)	77 mm (3.0 inches)	83%	moderate
December Weather	6°C (42°F)	81 mm (3.2 inches)	86%	moderate