In Texas and Louisiana, at least 30 people have died, more than 17,000 people are in shelters, hundreds of thousands are under evacuation orders, and all past U.S. rainfall records have been shattered, as Hurricane Harvey continues to wreak climate chaos in Houston, the fourth-largest city in the United States. Around 4 a.m. this morning, Harvey made landfall for a second time, just west of Cameron, Louisiana. In Texas, a third of Harris County—which encompasses Houston—is currently underwater. Houston officials have imposed a mandatory curfew between midnight and 5 a.m.

ExxonMobil says Harvey has damaged at least two of its refineries, causing thousands of pounds of chemicals to be released into the air. Residents in Crosby, Texas, are being evacuated amid concerns a chemical factory damaged by Harvey could explode. On Tuesday, the World Meteorological Organization’s spokesperson, Clare Nullis, explained how Harvey’s devastation is linked to climate change.

Clare Nullis: “What I think we can say is that the fact that we do have climate change—our atmosphere is warmer, it contains more moisture—it means that when we do have a hurricane, a tropical cyclone like this, then when an event does occur, then, you know, climate change does very likely increase the associated rainfall. But climate change per se does not cause tropical cyclones.”

This is the third 500-year flood to hit Houston in the last three years. By the time it’s finally over, the storm may be categorized as a once-in-a-thousand-year flood. Thousands of National Guardsmen have been mobilized to rescue stranded residents. Mexico has also offered to assist in the disaster response.