Don't wait until Atlanta gets too hot to plan a northern summer excursion.

Atlanta temperatures peaked at or above 90 degrees for 47 combined days between May and August, according to 2015 National Weather Service climate data.

This year, visit these nine major destinations along or east of the Mississippi River where cooler temperatures rarely topped 90 degrees. All cities listed have at least 300,000 residents and were at least five degrees cooler, on average, than Atlanta last year.

Indianapolis

81 degrees (6.6 degrees cooler than Atlanta)

Skip the Kentucky Bourbon Trail near Louisville and head to Indianapolis, where there were 24 fewer days last summer of extreme temperatures. The 100th running of The Indianapolis 500 takes place May 29, or go see NASCAR's Crown Royal 400 at the Brickyard on July 22-24.

Columbus, Ohio

80.5 degrees (7.1 degrees cooler than Atlanta)

The Ohio Statehouse and The Ohio State University provide plenty to do in Columbus, the state's largest city. The Columbus Commons, a downtown park also hosts concerts, movie screenings and fitness activities. Summer music series Picnic With The Pops starts June 17 and runs through July 30.

Pittsburgh

80.1 degrees (7.5 degrees cooler than Atlanta)

Whether it's the Three Rivers Arts Festival in June or the Pittsburgh Summer Beerfest in July, there is plenty to do in the Steel City without barely breaking a sweat. There is also Point State Park where the Great Allegheny Passage bike trail eventually links 355 miles all the way to Washington, D.C.

Detroit

79.1 degrees (8.2 degrees cooler than Atlanta)

Once left for dead, Detroit is making a comeback as a popular destination city. Summer is the ideal time to walk the Detroit River, cross the MacArthur Bridge and visit Belle Isle, a 985-acre state park separating the city from Canada.

Cleveland

78.2 degrees (9.4 degrees cooler than Atlanta)

Save The Rock and Roll Hall of Fame and Museum in Cleveland for the cold-weather months and instead tour the U.S.S. Cod Submarine Memorial and the Steamship William G. Mather, which is only open during the warm months at the Great Lakes Science Center on Lake Erie.

Chicago

77.4 degrees (10.2 degrees cooler than Atlanta)

The temperature met or topped 90 degrees in Chicago only seven times last year. The Lake Michigan beaches reopen May 27 and remain open through August, making any time this summer a great opportunity for some sun in the nation's third largest city.

Minneapolis

77.2 degrees (10.4 degrees cooler than Atlanta)

The larger of the Twin Cities offers plenty of water sports during the summer months, which rarely topped 90 degrees in 2015. Skip the nearby Mall of America and rent a boat on any of the thousand lakes surrounding the Minneapolis-St. Paul area.

Boston

77.4 degrees (11.4 degrees cooler than Atlanta)

The only major East Coast city cool enough to make the list, Boston's 10 hottest days occurred in July and August. That means it may be best to visit Beantown during the early summertime when there is a festival every weekend, including the Irish Fest Boston (June 4-5), the Boston Dragon Boat Festival (June 11-12) or Harborfest (July 1-4).

Milwaukee

74.3 degrees (13.3 degrees cooler than Atlanta)

This so-called "Little Chicago" keeps it cooler than The Windy City, with average monthly temperatures below 80 degrees last summer. Catch the annual Summerfest music spectacle June 29-July 3 and July 5-10 at Henry Maier Festival Park or another act at the busy lakeside venue.