Climate and monthly weather forecastKeystone, SD

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.

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 »