The eastern and central United States likely will see a greater risk of severe weather by the middle of this century as rising temperatures trigger atmospheric changes that favor storms, a new study by climate scientists from Stanford and Purdue universities concludes.

By the century’s final 30 years, the study forecasts, the eastern United States could experience severe thunderstorms an average of nearly 7.5 spring days, an increase of almost 42 percent. A 15 percent increase is forecast during June, July and August.

The largest single increase, an average of more than 2.4 days, was likely from March through May across parts of Texas, Oklahoma and Louisiana.

The study’s data suggest — but do not flatly predict — that the number of days with conditions favorable to tornadoes will increase as well.