The best times to visit Keystone for ideal weather are
June 18th to September 23rd
based on average temperature and humidity from NOAA (the National Oceanic and Atmospheric Administration). Read below for more weather and travel details.
Keystone Travel Guide
Other Keystone Travel Info
Weather in Keystone
Average temperatures in Keystone vary drastically. Considering humidity, temperatures feel cold for most of the year with a low chance of precipitation most of the year. The area is less temperate than some — in the 35th percentile for pleasant weather — compared to tourist destinations worldwide. Weeks with ideal weather are listed above. If you’re looking for the very warmest time to visit Keystone, the hottest months are July, August, and then June. See average monthly temperatures below. The warmest time of year is generally mid July where highs are regularly around 82.7°F (28.2°C) with temperatures rarely dropping below 54.6°F (12.6°C) at night.
Keystone Temperatures (Fahrenheit)
Keystone Temperatures (Celsius)
The way we experience weather isn’t all about temperature. Higher temperatures affect us much more at higher humidity, and colder temperatures feel piercing with high winds. Our perceived temperatures factor in humidity and wind chill to better represent how hot or cold the day feels to a person.
Keystone Perceived Temperature (F)
Keystone Perceived Temperature (C)
Average Keystone Temperatures by Month
Daily highs (averaged for the month) usually give the best indication of the weather. A significantly lower mean and low generally just means it gets colder at night.
|Month||Avg. High (°F)||Avg. Mean (°F)||Avg. Low (°F)|
|Month||Avg. High (°C)||Avg. Mean (°C)||Avg. Low (°C)|
Precipitation (Rain or Snow)
If dry weather is what you’re after, the months with the lowest chance of significant precipitation in Keystone are January, December, and then February. Note that we define “significant precipitation” as .1 inches or more in this section. The lowest chance of rain or snow occurs around mid January. For example, on the week of January 15th there are no days of precipitation on average. By contrast, it’s most likely to rain or snow in early to mid June with an average of 3 days of significant precipitation the week of June 11th.
When can you find snow in Keystone? Weather stations report no annual snow. Please note that a value of 0 for snow in the graph below may either mean there was no snow, or that snow is unreported.
Chance of Precipitation
The graph below shows the % chance of rainy and snowy days in Keystone.
Snow on the Ground
The graph below shows the average snow on the ground in Keystone (in).
Average Rain and Snow by Month
|Month||Daily Chance of Rain||Average Snow Depth (in)||Total Precipitation (in)|
|Month||Daily Chance of Rain||Average Snow Depth (cm)||Total Precipitation (cm)|
Humidity and Wind
Keystone has some comfortably humid months, and slightly dry months in the opposite season. The least humid month is September (39.8% relative humidity), and the most humid month is May (53.7%).
Wind in Keystone is usually calm. The windiest month is January, followed by May and April. January’s average wind speed of around 6.7 knots (7.7 MPH or 12.4 KPH) is considered “a light breeze.” Maximum sustained winds (the highest speed for the day lasting more than a few moments) are at their highest in late March where average top sustained speeds reach 14.5 knots, which is considered a moderate breeze.
Relative Humidity (%)
The graph below shows the average % humidity by month in Keystone.
The graph below shows wind speed (max and average) in knots.
Average Wind Speeds
Show Wind Speeds
All wind speeds are in knots. 1 knot = 1.15 MPH or 1.85 KPH.
|Month||Avg. Wind||Avg. Wind Feel||Sustained High Wind||High Wind Feel|
|Jan||6.7||Light breeze||13.6||Significant breeze|
|Feb||6||Light breeze||12.8||Significant breeze|
|Mar||6.2||Light breeze||13.4||Significant breeze|
|Apr||6.3||Light breeze||13.4||Significant breeze|
|May||6.4||Light breeze||13.6||Significant breeze|
|Jun||5.9||Light breeze||13.1||Significant breeze|
|Jul||5.1||Light breeze||11.8||Significant breeze|
|Aug||4.9||Light breeze||11.7||Significant breeze|
|Sep||5.1||Light breeze||11.6||Significant breeze|
|Oct||5.8||Light breeze||12.3||Significant breeze|
|Nov||5.9||Light breeze||12.4||Significant breeze|
|Dec||6||Light breeze||12.4||Significant breeze|
Show Relative Humidity by Month
|Month||Avg. Relative Humidity|
Is it Safe to Travel to Keystone?
Our best data indicates this area is generally safe. As of Oct 07, 2019 there are no travel advisories or warnings for the United States; exercise normal security precautions. Check this page for any recent changes or regions to avoid: Travel Advice and Advisories. This advisory was last updated on Sep 23, 2019.
The Busiest and Least Crowded Months
The busiest month for tourism in Keystone, SD, US is August, followed by September and May. Prices for hotels and flights will be most expensive during these months, though you can save if you purchase well in advance. Tourists are unlikely to visit Keystone in October. Those willing to visit at these times will likely find it the least expensive month.
Estimated Tourism by Month
Most Popular Months to Visit
Overall Keystone Travel Experience by Season
Spring (March through May)
Humidity and temperatures combine to make this season feel moderately cold. Highs range from 66.8°F (19.3°C) and 37.7°F (3.2°C) with warmer temperatures in the later months. Rain is somewhat common with 3 to 8 days of significant precipitation per month. Spring is fairly slow for tourism, which makes it a good time for those looking for deals.
Summer (June through August)
The middle-year months have very comfortable weather with high temperatures that are comfortable. These months see the most precipitation with 5 to 9 days of precipitation per month. June – August is the busiest season for tourism in Keystone, so lodging and other accommodations may cost more than usual.
Fall (September through November)
Fall daily highs range from 75.5°F (24.2°C) and 39.8°F (4.3°C), which will feel chilly given the humidity and wind. It rains or snows a normal amount: 2 to 4 days per month. Tourism is the slowest during these months due to the weather, so hotels may be affordably priced.
Winter (December through February)
Weather is far too cold this time of year in Keystone to be enjoyable for warm weather travelers. The average high during this season is between 37.7°F (3.2°C) and 32.2°F (0.1°C). On average, it rains or snows a smalll amount: 1 to 2 times per month. These times of year are the second busiest with tourists.