May weather forecastKeystone, SD
May
Weather in May
As May rolls around, Keystone residents can finally bask in the warmth of the Spring season. Substantial rainfall of 3.11" (79mm) becomes evident in the city's weather records, making this the peak rainfall month of the year. People can fully enjoy the refreshing season as longer daylight hours and ascending temperatures make conditions favorable for outdoor activities. The gutters sing with rainfall as the smell of wet earth fills the air. As May morphs into June, Keystone looks forward to the much-awaited onset of summer, bringing longer, sunnier and drier days.Temperature
Keystone sees an increase in the average high-temperature with the arrival of May, moving from April's cool 50.9°F (10.5°C) to a refreshing 61°F (16.1°C). Keystone records an average temperature drop to a wintry 42.4°F (5.8°C) in May.Humidity
In Keystone, the average relative humidity in May is 66%.Rainfall
In Keystone, during May, the rain falls for 18.6 days and regularly aggregates up to 3.11" (79mm) of precipitation. Throughout the year, there are 135.4 rainfall days, and 20.39" (518mm) of precipitation is accumulated.Snowfall
January through May, September through December are months with snowfall. May is the last month it regularly snows. During 3.4 snowfall days, in May, Keystone aggregates 4.09" (104mm) of snow. In Keystone, during the entire year, snow falls for 75.1 days and aggregates up to 40.24" (1022mm) of snow.Daylight
In Keystone, South Dakota, the average length of the day in May is 14h and 46min.On the first day of the month, sunrise is at 5:44 am and sunset at 7:57 pm. On the last day of May, sunrise is at 5:14 am and sunset at 8:28 pm MDT.
Sunshine
In May, the average sunshine is 10.1h.UV index
The average daily maximum UV index in May is 4. A UV Index of 3 to 5 symbolizes a medium vulnerability from exposure to the Sun's UV rays for the average person.Note: In May, the maximum UV index of 4 transforms into these recommendations:
Adopt protective measures - Suggestions to resist sunburn are offered. Being exposed to the midday Sun can have harmful effects due to strong UV radiation; always take precautions. On days when the sun blazes, arm yourself with sunglasses that block UVA and UVB radiation. Watch out! The Sun's UV radiation can be nearly magnified twofold due to snow reflection.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in May
Keystone, SD
- Average high temperature in May: 61°F
The warmest month (with the highest average high temperature) is July (81.7°F).
The month with the lowest average high temperature is December (29.8°F).
- Average low temperature in May: 42.4°F
The month with the highest average low temperature is July (60.4°F).
The coldest month (with the lowest average low temperature) is February (16.2°F).
Average pressure in May
Keystone, SD
- Average pressure in May: 29.91"Hg
The month with the highest atmospheric pressure is January (30.13"Hg).
The month with the lowest atmospheric pressure is June (29.84"Hg).
Average wind speed in May
Keystone, SD
- Average wind speed in May: 8.9mph
The windiest month (with the highest average wind speed) is April (9.5mph).
The calmest month (with the lowest average wind speed) is August (7mph).
Average humidity in May
Keystone, SD
- Average humidity in May: 66%
The months with the highest relative humidity are January and February (77%).
The months with the lowest relative humidity are August and September (52%).
Average rainfall in May
Keystone, SD
- Average rainfall in May: 3.11"
The wettest month (with the highest rainfall) is June (3.19").
The driest month (with the least rainfall) is January (0.47").
Average rainfall days in May
Keystone, SD
- Average rainfall days in May: 18.6 days
The month with the highest number of rainy days is May (18.6 days).
The month with the least rainy days is November (4.5 days).
Average snowfall in May
Keystone, SD
- Average snowfall in May: 4.09"
The month with the highest snowfall is April (7.24").
The months with the least snowfall are June, July and August (0").
Average snowfall days in May
Keystone, SD
- Average snowfall days in May: 3.4 days
The month with the highest number of snowfall days is February (12.9 days).
The months with the least snowfall days are June, July and August (0 days).
Average daylight in May /
Average sunshine in May
Keystone, SD
- Average daylight in May: 14h and 48min
The month with the longest days is June (Average daylight: 15h and 24min).
The month with the shortest days is December (Average daylight: 9h and 0min).
- Average sunshine in May: 10h and 6min
The month with the most sunshine is August (Average sunshine: 11h and 42min).
The month with the least sunshine is February (Average sunshine: 6h and 0min).
Average sunshine days in May
Keystone, SD
- Average sunshine days in May: 7.8 days
The month with the most sunshine days is November (19.2 days).
The month with the least sunshine days is May (7.8 days).
Average UV index in May
Keystone, SD
- Average UV index in May: 4
The month with the highest UV index is July (UV index 6).
The months with the lowest UV index are January, February, March, October, November and December (UV index 2).
Average cloud cover in May
Keystone, SD
- Average cloud cover in May: 35
The month with the most cloud cover is April (Cloud cover 38).
The month with the least cloud cover is August (Cloud cover 17).
Average visibility in May
Keystone, SD
- 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).
