May weather forecastGrafton, IL
May
Weather in May
The last month of the spring, May, is a moderately hot month in Grafton, Illinois, with an average temperature varying between 56.8°F (13.8°C) and 74.1°F (23.4°C).Temperature
The onset of May brings a temperature shift, with the average high-temperature moving from a refreshing 64.9°F (18.3°C) in April to a warm 74.1°F (23.4°C). In May, the recorded average low-temperature in Grafton is a mild 56.8°F (13.8°C).Humidity
May is the most humid month, with an average relative humidity of 79%.Rainfall
The month with the most rainfall is May, when the rain falls for 15.9 days and typically aggregates up to 3.35" (85mm) of precipitation.Snowfall
April through October are months without snowfall.Daylight
The average length of the day in May is 14h and 19min.On the first day of May in Grafton, sunrise is at 6:02 am and sunset at 7:54 pm. On the last day of the month, sunrise is at 5:38 am and sunset at 8:21 pm CDT.
Sunshine
In May, the average sunshine in Grafton is 9.3h.UV index
The months with the highest UV index are May through August, with an average maximum UV index of 6. A UV Index reading of 6 to 7 represents a high health vulnerability from unsafe exposure to UV radiation for the average person.Note: The maximum UV index of 6 during May leads to these instructions:
Steer clear of overexposure. Fair-skinned individuals can be scorched in less than 20 minutes. Stay out of direct sunlight between 10 a.m. and 4 p.m., when UV radiation is most intense, and remember that not all shade structures provide complete protection. For a sun-safe wardrobe, go for clothes that are tightly woven and generously sized.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in May
Grafton, IL
- Average high temperature in May: 74.1°F
The warmest month (with the highest average high temperature) is July (86.4°F).
The month with the lowest average high temperature is January (36.1°F).
- Average low temperature in May: 56.8°F
The month with the highest average low temperature is July (68.2°F).
The coldest month (with the lowest average low temperature) is January (23.4°F).
Average pressure in May
Grafton, IL
- Average pressure in May: 29.95"Hg
The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is June (29.92"Hg).
Average wind speed in May
Grafton, IL
- Average wind speed in May: 7.4mph
The windiest month (with the highest average wind speed) is January (9.4mph).
The calmest months (with the lowest average wind speed) are July and August (5.7mph).
Average humidity in May
Grafton, IL
- Average humidity in May: 79%
The month with the highest relative humidity is May (79%).
The month with the lowest relative humidity is October (71%).
Average rainfall in May
Grafton, IL
- Average rainfall in May: 3.35"
The wettest month (with the highest rainfall) is May (3.35").
The driest month (with the least rainfall) is February (1.3").
Average rainfall days in May
Grafton, IL
- Average rainfall days in May: 15.9 days
The month with the highest number of rainy days is July (16.3 days).
The month with the least rainy days is January (6.3 days).
Average snowfall in May
Grafton, IL
- Average snowfall in May: 0"
The months with the highest snowfall are January and February (1.54").
The months with the least snowfall are April, May, June, July, August, September and October (0").
Average snowfall days in May
Grafton, IL
- Average snowfall days in May: 0 days
The month with the highest number of snowfall days is January (5.7 days).
The months with the least snowfall days are May, June, July, August and September (0 days).
Average daylight in May /
Average sunshine in May
Grafton, IL
- Average daylight in May: 14h and 18min
The month with the longest days is June (Average daylight: 14h and 54min).
The month with the shortest days is December (Average daylight: 9h and 30min).
- Average sunshine in May: 9h and 18min
The months with the most sunshine are June and July (Average sunshine: 10h and 24min).
The months with the least sunshine are January and February (Average sunshine: 4h and 36min).
Average sunshine days in May
Grafton, IL
- Average sunshine days in May: 12.7 days
The month with the most sunshine days is December (19.8 days).
The month with the least sunshine days is June (11.2 days).
Average UV index in May
Grafton, IL
- Average UV index in May: 6
The months with the highest UV index are May, June, July and August (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 2).
Average cloud cover in May
Grafton, IL
- Average cloud cover in May: 38
The month with the most cloud cover is January (Cloud cover 51).
The month with the least cloud cover is August (Cloud cover 28).
Average visibility in May
Grafton, IL
- Average visibility in May: 6mi
The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
