The oceans are full of heat, and it’s coming ashore

This summer's heat is coming from the ocean as much as the sky. The world's oceans just had their hottest June on record, with nearly 40 percent of ocean area caught in a marine heatwave. Some patches in the Mediterranean and Pacific are running more than 10 degrees Fahrenheit above normal. That matters on land because warm ocean water and air feed directly into heatwaves, humidity, and storms. Scientists estimate at least a fifth of heatwaves on land start in the ocean. Warm water off Florida's Gulf coast, for instance, is tied to the muggy heat pushing up air-conditioner use there, and unusual Pacific warmth may be feeding into a heatwave forecast for the central and northern U.S.

Warmer air also holds more moisture, meaning longer dry stretches between rains and heavier downpours when rain does come. Ocean warming adds to sea level rise too, through thermal expansion, which lets storms push farther inland along coastlines.

On top of this, a strong El Niño, a recurring warm-water pattern in the Pacific, is building and has a high chance of becoming one of the strongest on record. El Niño years tend to bring heavier rain to places like California and drier conditions to Australia and Southeast Asia, and scientists expect global temperatures to stay elevated into next year as a result. None of this points to one specific fix for a house, but it helps explain why summers are bringing more extreme heat, heavier storms, and higher humidity to many parts of the country at once.