WASHINGTON — This probably comes as no surprise: Federal scientists say July was the hottest month ever recorded in the Lower 48 states, breaking a record set during the Dust Bowl of the 1930s.

And even less a surprise: The United States this year keeps setting records for weather extremes, based on the precise calculations that include drought, heavy rainfall, unusual temperatures, and storms.

The average temperature last month was 77.6 degrees. That breaks the old record from July 1936 by 0.2 degree, according to the National Oceanic and Atmospheric Administration. Records go back to 1895.

‘‘It’s a pretty significant increase over the last record,’’ said climate scientist Jake Crouch of NOAA’s National Climatic Data Center in Asheville, N.C. In the past, skeptics of global warming have pointed to the Dust Bowl to argue that recent heat isn’t unprecedented. But Crouch said this shows that the current year ‘‘is out and beyond those Dust Bowl years. We’re rivaling and beating them consistently from month to month.’’

Three of the nation’s five hottest months on record have been recent Julys: This year, 2011, and 2006. Julys in 1936 and 1934 round out the top five.