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Study: Rapid City has nation's most unpredictable weather

Study: Rapid City has nation's most unpredictable weather


Rapid City might be the best place in the United States to be a weather forecaster.

That's because it has the handiest excuse for bad predictions.

According to an analysis published Thursday by nationally known statistician Nate Silver on his FiveThirtyEight website, Rapid City has the most unpredictable weather in the country.

Of Rapid City's wild meteorological swings, Silver wrote: "Its temperature might be 30 degrees in January — or just as easily -12. It’s snowy and windy and prone to big, unexpected winter storms. And it has a thunderstorm on almost 25 percent of days from July through September, more than the national average.”

In one respect, his analysis is a sucker punch at a region, not merely Rapid City. Of the first 25 on his most-unpredictable list, South Dakota, Montana, North Dakota, Nebraska, Wyoming and Kansas fill 14 of the slots, with Sioux Falls and Aberdeen joining Rapid City in the top eight.

Similarly, the most predictable cities share both geography and a characteristic: heat, some of it blazing. Honolulu predictably heads that list, and the others in the top 10 are in California, Arizona, Florida and southern Nevada.

Silver's analysis compared daily weather patterns against long-term averages at 120 National Weather Service stations around the country.

Susan Sanders, warning coordination meteorologist at the National Weather Service office in Rapid City, said the analysis reflects the unpredictability that she sees on a daily basis.

“We don’t use it as an excuse for blowing a forecast,” Sanders said, “but we realize there are going to be variations, and we work as hard as we can to be as accurate as possible.”

Examples of weather events to support Silver’s analysis abound, perhaps none more conspicuous than 2013’s early October blizzard, which brought more snow to Rapid City in a few days — about 2 feet — than the city had received in any previous full month of October.

Sanders didn’t have to search long for more examples. Today’s almanac shows a record Dec. 5 high of 67 degrees in Rapid City and a record low of 22-below, a massive variation of 89 degrees.

Most deserving of blame for the unpredictability is Rapid City’s location next to the Black Hills, which rise thousands of feet above the surrounding plains.

“Because it’s an isolated mountain range, weather can go around it or over it,” Sanders said. “And so it causes a lot of variation in a very small area.”

It all adds up to horrible-sounding weather, but statistics belie what locals know from experience: Rapid City has some of the best all-around weather in the state. Sure, it’s unpredictable, but compared with the rest of the state, it’s also warmer in the winter and less humid in the summer.

So while Nate Silver advises residents of Chicago or Denver who are tired of their unpredictable weather to “be thankful you don’t have to deal with the (weather) they have in Rapid City,” Sanders said unpredictability is just one part of Rapid City’s weather profile.

“I think people enjoy the weather out here,” she said.

Contact Seth Tupper at

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