I think somewhere in Montana holds the U.S. record for a 24 hour swing 78 F seems to stick in my mind. For a month swing my town tops this list.
1. Casper, Wyoming: 99 degrees (high 72, low -27)
2. Lander, Wyoming: 89 degrees (high 71, low -18)
3. Great Falls, Montana: 88 degrees (high 66, low -22)
4. (tie) Sheridan, Wyoming: 87 degrees (high 70, low -17)
4. (tie) Valentine, Nebraska: 87 degrees (high 73, low -14)
6. (tie) Denver, Colorado: 86 degrees (high 72, low -14)
6. (tie) Goodland, Kansas: 86 degrees (high 80, low -6)
8. Aberdeen, South Dakota: 85 degrees (high 68, low -17)
9. (tie) Havre, Montana: 84 degrees (high 65, low -19)
9. (tie) Pueblo, Colorado: 84 degrees (high 75, low -9)
11. Norfolk, Nebraska: 82 degrees (high 77, low -5)
12. Grand Island, Nebraska: 81 degrees (high 78, low -3)
13. (tie) Bismarck, North Dakota: 80 degrees (high 66, low -14)
13. (tie) Cheyenne, Wyoming: 80 degrees (high 66, low -14)
NWS