See the trend in hot days in these U.S. cities.
A small increase in average temperature leads to a big increase in extreme heat.
The first day with summer-like temperatures is happening earlier for most of these cities.
The amount of carbon dioxide in the atmosphere has a strong correlation with rising temperatures.
Since the first Earth Day in 1970, the average annual temperature in every state has climbed.
More water is flowing this year in California from frequent storms and melting snowpack.
Western snowpack at the end of the the wet season is up this year — but that's less likely in the future.
Snow cover in North America is on the decline in part due to climate change.