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Contents
- The climate of Keystone
- The best time to visit Keystone
- The worst time to visit Keystone
- Spring weather in Keystone
- Summer weather in Keystone
- Autumn weather in Keystone
- Winter weather in Keystone
- Weather in January
- Weather in February
- Weather in March
- Weather in April
- Weather in May
- Weather in June
- Weather in July
- Weather in August
- Weather in September
- Weather in October
- Weather in November
- Weather in December
- Frequently asked questions
- Average temperature
- Average pressure
- Average wind speed
- Average humidity
- Average rainfall
- Average rainfall days
- Average snowfall
- Average snowfall days
- Average daylight
- Average sunshine
- Average sunshine days
- Average UV index
- Average cloud cover
- Average visibility
The climate of Keystone
Based on the Köppen climate classification, Keystone, South Dakota is situated within the BSk climate zone, characterized by the mid-latitude steppe. This zone typically experiences a significant temperature disparity between seasons, with hot summers and cold, often snow-filled winters. Keystone predominantly oscillates between temperature lows of approximately 16.2°F (-8.8°C) in February and highs of around 81.7°F (27.6°C) in July, reflecting considerable seasonal variation.
In terms of rainfall, the precipitation peaks happen from May to August with June recording the highest rainfall at 3.19" (81mm). On the other hand, December and January are typically the driest months, with a scant 0.47" (12mm) and 0.67" (17mm) of rainfall, respectively. Interestingly, while June is the wettest, it also offers longest daylight duration of approximately 15.4 hours. Furthermore, Keystone’s geographical location makes it a wind-prone area, with average wind speed varying from 7mph (11.3km/h) in August to 9.5mph (15.3km/h) in April.
Snowfall is another feature of Keystone’s climate, most notably from January through April, with March witnessing the highest average snowfall of 7.24" (184mm). In contrast, from June to September, there is virtually no snowfall to be seen. With regards to sunshine, July stands out with the most sunlit days, boasting 11.6 hours of sunshine.
In terms of rainfall, the precipitation peaks happen from May to August with June recording the highest rainfall at 3.19" (81mm). On the other hand, December and January are typically the driest months, with a scant 0.47" (12mm) and 0.67" (17mm) of rainfall, respectively. Interestingly, while June is the wettest, it also offers longest daylight duration of approximately 15.4 hours. Furthermore, Keystone’s geographical location makes it a wind-prone area, with average wind speed varying from 7mph (11.3km/h) in August to 9.5mph (15.3km/h) in April.
Snowfall is another feature of Keystone’s climate, most notably from January through April, with March witnessing the highest average snowfall of 7.24" (184mm). In contrast, from June to September, there is virtually no snowfall to be seen. With regards to sunshine, July stands out with the most sunlit days, boasting 11.6 hours of sunshine.
The best time to visit Keystone
The optimal time for a visit to Keystone would be between May to September. During these months, the weather blossoms, as the average temperatures hover between a comfortable 50.9°F (10.5°C) to 80.1°F (26.7°C). While rainfall does hit its peak during these months, the daily duration of sunshine also shows an increase, compensating for the precipitation. This period also experiences longer daylight hours, allowing visitors to explore the beautiful outdoors for a more extended period.
The worst time to visit Keystone
The period from November through March may not be the most hospitable for visitors. During these months, the temperatures plummet, reaching a frigid low of about 16.5°F (-8.6°C) in December. Moreover, these months also witness considerable snowfall averaging between 3.54" (90mm) in January and a peak of 7.24" (184mm) in March, which may hinder outdoor activities.
Spring weather in Keystone
Spring, which runs from March to May in Keystone, brings gradual warmth after the winter chills. The temperature rises from 43.9°F (6.6°C) to 61°F (16.1°C). Although it starts as a relatively dry season in March with only 1.34" (34mm) of rainfall, by May, precipitation increases to 3.11" (79mm). It is also during this period that daylight hours increase from 12 hours in March to a generous 14.8 hours in May.
Summer weather in Keystone
Summer in Keystone reigns from June to August, showcasing high temperatures from 74.1°F (23.4°C) up to a scorching 81.7°F (27.6°C). Although rainfall peaks in this period, the season is also host to the longest daylight duration of approximately 15.4 hours in June, allowing for ample outdoor activities. Average wind speeds decrease slightly during this period making the temperatures seem even warmer.
Autumn weather in Keystone
Autumn which sets in September through November records a decrease in temperature from 71.4°F (21.9°C) to 42.3°F (5.7°C). Precipitation also tapers off, from 1.22" (31mm) in September down to 0.63" (16mm) in November. Throughout the season, wind speeds gradually increase, reaching an average high of 9.1mph (14.6km/h) in November.
Winter weather in Keystone
Winter in Keystone, spanning December to February, observes a dramatic drop in temperatures, fluctuating between a low of 16.5°F (-8.6°C) to a high of 31.5°F (-0.3°C). While precipitation is modest during these months, snowfall dominates, with January and February recording 3.54" (90mm) and 5.71" (145mm) of snow respectively, resulting in a snow-covered landscape. These months also experience the lowest daylight duration, decreasing to a yearly low of 9 hours in December.
Weather in January
In Keystone, South Dakota, the year unfolds with chilly weather, making January a cold month compared to subsequent ones. The mercury drops to around 17.1°F (-8.3°C) in the early mornings, marking this as the lowest average temperature of the year. Weather in January »
Weather in February
The cold weather continues to dominate in Keystone throughout February, only slightly less harsh than in January. The second month is distinguished by the highest average snowfall of the year, with 5.71" (145mm) covering this North American city. Weather in February »
Weather in March
March in Keystone signals the advent of Spring, which begins to modify the weather conditions seen in the previous two months. The most notable difference in March is a leap in temperature, with highs reaching up to 43.9°F (6.6°C), establishing it as a transitional month. Weather in March »
Weather in April
The weather in Keystone further improves in April, providing a relief from the freezing winter months. The highest increase is seen in temperatures, with April featuring a high of 50.9°F (10.5°C), signaling the imminent arrival of summer. Weather in April »
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. Weather in May »
Weather in June
June sees Keystone, South Dakota celebrating summer with a significant leap in ambient temperature. The average temperature continues to climb, achieving a hot 74.1°F (23.4°C) this month, signaling the full swing of summer. It is about this time that, with the sun high up most of the day, outdoor activities become increasingly enjoyable. Weather in June »
Weather in July
Warm and comfortable would accurately describe the weather in Keystone for the month of July. The city records its highest temperatures for the year during this month, with a top temperature reaching a scorching 81.7°F (27.6°C). Weather in July »
Weather in August
In Keystone, August bears the traits of a typical late summer month, showcasing warm days and relatively cooler nights. Maximum temperatures drop slightly to 80.1°F (26.7°C), indicating the slow transition towards fall. Rain showers during this month are less frequent, making this an enjoyable period for visitors and locals. Weather in August »
Weather in September
September in Keystone introduces the initial hints of the fall season, evident in the drop in temperatures and shortening daylight hours. Temperatures begin their descent with highs hitting around 71.4°F (21.9°C), a direct contrast to the sizzling heat of August. Weather in September »
Weather in October
October is a transitional period for Keystone city weather with decreasing temperatures and a remarkable increase in rainfall rates. A significant drop in average temperature is noted with highs of around 54°F (12.2°C), indicating the gradual onset of winter. Weather in October »
Weather in November
The weather in Keystone, South Dakota turns noticeably colder in November, as winter approaches and the fall season draws to a close. Snowfall re-appears with an average of 4.09" (104mm), marking the beginning of the winter season for the city. Weather in November »
Weather in December
December marks the commencement of the freezing winter season in Keystone, South Dakota. The average high temperature drops to a chilly 29.8°F (-1.2°C), making December one of the coldest months of the year. Snowfall sights become more frequent, blanketing the region with a white layer, while creating a picture-perfect winter wonderland. Weather in December »
Updated: Aug 25, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What are the most humid months?
The months with the highest humidity are January and February, with an average relative humidity of 77%.
What is the driest month?
The month with the least rainfall is January, when the rain falls for 6.2 days and typically collects 0.47" (12mm) of precipitation.
How many days does it rain in Keystone?
In Keystone, during the entire year, the rain falls for 135.4 days and collects up to 20.39" (518mm) of precipitation.
When does it snow?
January through May, September through December are months with snowfall.
How much does it snow?
Throughout the year, there are 75.1 snowfall days, and 40.24" (1022mm) of snow is accumulated.
What are the months with the lowest UV index?
The months with the lowest UV index are January through March, October through December, with an average maximum UV index of 2.
What is the month with the least sunshine?
The month with the least sunshine is February, with an average of 6h of sunshine.
When is Daylight Saving Time (DST)?
On Sunday, March 10. 2024, at 2:00 am, Daylight Saving Time starts in Keystone, and the time zone changes from MST to MDT. Daylight Saving Time ends Sunday, November 3. 2024, at 2:00 am, and the time zone reverts from MDT to MST.
When does it snow the most?
The month with the most snowfall is April, when snow falls for 8.8 days and typically aggregates up to 7.24" (184mm) of snow.
What is the rainiest month?
June is the month with the most rainfall. Rain falls for 18 days and accumulates 3.19" (81mm) of precipitation.
When it does not snow?
June through August are months without snowfall.
When are the longest days?
June has the longest days of the year, with an average of 15h and 24min of daylight.
What part of the year is the hottest?
The warmest temperatures occur during July, when averages reach a peak of 81.7°F (27.6°C) and a low of 60.4°F (15.8°C).
What is the month with the highest UV index?
July is the month with the highest UV index, with an average maximum UV index of 6.
What are the least humid months?
The months with the lowest humidity are August and September, with an average relative humidity of 52%.
What month has the most sunshine?
The month with the most sunshine is August, with an average of 11.7h of sunshine.
What is the coldest time of year?
December stands out as Keystone's coldest month, with an average high-temperature of 29.8°F (-1.2°C) and a low-temperature of 16.5°F (-8.6°C).
What is the month with the shortest days?
The month with the shortest days is December, with an average of 9h and 0min of daylight.
Average temperature
Keystone, SD
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).
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
Keystone, SD
- Average pressure in January:
30.13"Hg - Average pressure in February:
30.11"Hg - Average pressure in March:
30"Hg - Average pressure in April:
29.92"Hg - Average pressure in May:
29.91"Hg - Average pressure in June:
29.84"Hg
- Average pressure in July:
29.9"Hg - Average pressure in August:
29.9"Hg - Average pressure in September:
29.93"Hg - Average pressure in October:
29.98"Hg - Average pressure in November:
30.05"Hg - Average pressure in December:
30.12"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
Keystone, SD
- Average wind speed in January:
9.2mph - Average wind speed in February:
8.8mph - Average wind speed in March:
8.8mph - Average wind speed in April:
9.5mph - Average wind speed in May:
8.9mph - Average wind speed in June:
8.3mph
- Average wind speed in July:
7.5mph - Average wind speed in August:
7mph - Average wind speed in September:
8.1mph - Average wind speed in October:
9.1mph - Average wind speed in November:
8.6mph - Average wind speed in December:
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
Keystone, SD
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
Keystone, SD
- Average rainfall in January:
0.47" - Average rainfall in February:
0.83" - Average rainfall in March:
1.34" - Average rainfall in April:
2.32" - Average rainfall in May:
3.11" - Average rainfall in June:
3.19"
- Average rainfall in July:
2.91" - Average rainfall in August:
2.56" - Average rainfall in September:
1.22" - Average rainfall in October:
1.14" - Average rainfall in November:
0.63" - Average rainfall in December:
0.67"
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
Keystone, SD
- Average rainfall days in January:
6.2 days - Average rainfall days in February:
6.3 days - Average rainfall days in March:
9.3 days - Average rainfall days in April:
13.3 days - Average rainfall days in May:
18.6 days - Average rainfall days in June:
18 days
- Average rainfall days in July:
17.3 days - Average rainfall days in August:
16.6 days - Average rainfall days in September:
10 days - Average rainfall days in October:
9 days - Average rainfall days in November:
4.5 days - Average rainfall days in December:
6.3 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
Keystone, SD
- Average snowfall in January:
3.54" - Average snowfall in February:
5.71" - Average snowfall in March:
6.97" - Average snowfall in April:
7.24" - Average snowfall in May:
4.09" - Average snowfall in June:
0"
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
Keystone, SD
- Average snowfall days in January:
12.3 days - Average snowfall days in February:
12.9 days - Average snowfall days in March:
11.3 days - Average snowfall days in April:
8.8 days - Average snowfall days in May:
3.4 days - Average snowfall days in June:
0 days
- Average snowfall days in July:
0 days - Average snowfall days in August:
0 days - Average snowfall days in September:
0.4 days - Average snowfall days in October:
5.3 days - Average snowfall days in November:
9.2 days - Average snowfall days in December:
11.5 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 / Average sunshine
Keystone, SD
- Average daylight in January:
9h and 2min - Average daylight in February:
10h and 3min - Average daylight in March:
12h and 0min - Average daylight in April:
13h and 3min - Average daylight in May:
14h and 5min - Average daylight in June:
15h and 2min
- Average daylight in July:
15h and 1min - Average daylight in August:
13h and 5min - Average daylight in September:
12h and 3min - Average daylight in October:
11h and 0min - Average daylight in November:
9h and 4min - Average daylight in December:
9h and 0min
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 January:
6h and 2min - Average sunshine in February:
6h and 0min - Average sunshine in March:
7h and 5min - Average sunshine in April:
9h and 3min - Average sunshine in May:
10h and 1min - Average sunshine in June:
11h and 2min
- Average sunshine in July:
11h and 4min - Average sunshine in August:
11h and 4min - Average sunshine in September:
10h and 3min - Average sunshine in October:
7h and 1min - Average sunshine in November:
6h and 4min - Average sunshine in December:
6h and 1min
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
Keystone, SD
- Average sunshine days in January:
17.4 days - Average sunshine days in February:
13.8 days - Average sunshine days in March:
13.3 days - Average sunshine days in April:
9.8 days - Average sunshine days in May:
7.8 days - Average sunshine days in June:
7.9 days
- Average sunshine days in July:
8.6 days - Average sunshine days in August:
9.9 days - Average sunshine days in September:
17.3 days - Average sunshine days in October:
17.4 days - Average sunshine days in November:
19.2 days - Average sunshine days in December:
18.1 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
Keystone, SD
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
Keystone, SD
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
Keystone, SD
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).
Keystone, South Dakota, USA
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