This interactive map from Climate Central has the average temperatures of each state and how they've changed since the first Earth day in 1970. Click on a state to see its graph. The states that have warmed the most since then are Delaware and Wisconsin, at about 3 degrees warmer than in 1970.
Average temperatures across most of the continental U.S. have been rising gradually for more than a century, at a rate of about 0.127°F per decade between 1910-2012. That trend parallels an overall increase in average global temperatures, which is largely the result of human greenhouse gas emissions. While global warming isn’t uniform, and some regions are warming faster than others, since the 1970s, warming across the U.S. has accelerated, previously shown in our report The Heat is On. Since then, every state’s annual average temperature has risen accordingly. On average, temperatures in the contiguous 48 states have been warming at a rate of 0.48°F per decade since 1970, nearly twice the global average.
You can find a chart to compare the warming among the states at Climate Central.