As you may have posted this a while ago and may not look at the site again for a while, it is hard to tell you what the hottest place in USA today. I can, however, let you know the history of warm states and cities and what is likely to be the warmest place in America.
In general, the warmest states on average per year in America are;
The warmest place in the winter each year is Miami in Florida. It's average winter temperature is 21 degrees Celsius and when Miami is around this temperature, the more northern states are sometimes below freezing and have snowy periods. This makes Florida an ideal winter holiday destination if you wish to visit hotter climates and are bored of the frosty weather in the north.
Some people wish to visit colder states in the winter to experience the snow and feel more traditional at Christmas. New York is a popular destination in the United States during the winter and as it is so close to Canada, many people also cross over to Canada to experience their winter temperatures too.
The hottest recorded temperature in the United States of America is in Greenland Ranch California back in 1913. The temperature reached 134 degrees Farenheit and this temperature has not been recorded since anywhere in the country.
As the southern states are closer to the equator, they do tend to see much hotter summers and even their winter temperatures are equivalent to a cool summers day in more northerly states. Although this is great for the people living and visiting there, it is also great for the American economy as tourists do not have to leave the USA to find a holiday destination that will fulfill their climate needs.