That's according to a survey released today by the group Iraq and Afghanistan Veterans of America (IAVA).
As you may have heard, 2012 was the hottest year ever recorded in the U.S.
Australia is also seeing higher temperatures.
The average nationwide temperature for Australia earlier this week was a near-record of 105 degrees, adding fuel to the raging wildfires across the country.
So far no deaths have been reported from the fires, but 100 people haven’t been accounted for since a blaze destroyed around 90 homes last week.
It cooled off a bit today, but forecasters say temperatures are expected rise again by week’s end.
From Sydney, the BBC’s Phil Mercer reports.