Most states in the U.S. have begun witnessing a dramatic increase in dangerous heat days since the 1970s and they could double across the country by 2050.

A study by Climate Central, States at Risk, shows that the hottest parts of the country, including Texas, Arizona, Colorado and Florida have seen the largest increase in extreme heat days, which include high temperatures and high humidity.

In Florida, which faces the greatest risk of rising temperatures, cities such as Miami, Tampa and Naples will see 100-plus days of extreme heat by 2050.

Extreme Heat

Extreme heat is the most pervasive threat, affecting every state, particularly in the Southeast and along the Gulf Coast where the combination of heat and humidity is projected to cross thresholds dangerous for human health within the next decade. Compared with today, by 2050, 11 states are projected to have an additional 50 or more heat wave days per year, two will have an additional 60, and Florida is expected to have 80. Extreme heat is the threat where states are least prepared overall; only seven states have taken strong action to prepare for extreme heat risks.

Summer Drought

Texas currently faces the highest overall summer drought threat of any state, by a substantial margin. By 2050, however, nine states—Colorado, Idaho, Montana, New Mexico, Texas, Michigan, Wisconsin, Minnesota, and Washington—are projected to face a greater summer drought threat than Texas does today. Some, like Colorado, Washington, and Michigan, are reasonably well prepared overall, earning a B or higher based on their good understanding of the risks they face and plans they have made for adaptation. Others, like Texas and Montana have taken little action, scoring a D- and an F respectively.

Wildfires

The growing threat from wildfires is concentrated in four states, Texas, California, Arizona, and Nevada, where more than 35 million people live in the high threat zone where wildlands and development converge. But climate-driven wildfire threats are not restricted to Western states. Florida, North Carolina and Georgia combine for another 15 million people at risk, and four Southeastern states, Arkansas, Alabama, Louisiana, and Mississippi, all face above average increases in wildfire risks by 2050. Current preparedness for wildfires is very high, but future threats are poorly understood or planned for; 15 of the 24 states analyzed do not have a climate adaptation plan that includes wildfires.

Inland Flooding

Florida and California have the largest vulnerable populations at risk with 1.5 and 1.3 million people living in the inland FEMA 100-year floodplain respectively. Georgia is third most at risk with 570,000 people. More than half of all states assessed (17 out of 32) have taken no action to plan for future climate change related inland flooding risks or implemented strategies to address them.

Coastal Flooding

Florida and Louisiana face enormous coastal flooding risks, far greater than any of the other 22 coastal states. Florida alone has 4.6 million people projected at risk (living in the100-year coastal floodplain) by 2050. Louisiana has 1.2 million. Overall, states are more prepared for coastal flooding than for any other threat. Florida, however, is not among them. Florida earned an F for coastal flood preparedness, due to its average level of readiness in the face of enormous current and future risks. Louisiana, which is far better prepared, earned a B-.

For a deeper dive: Climate Central, Miami Herald, Time Warner Cable News, Valley Central, Colorado Public Radio, StateImpact