A boy hugs his grandmother’s dog after being rescued from rising floodwaters in Spring, Tex., on Monday as devastation from Hurricane Harvey continued. (Luke Sharrett/Bloomberg)

AFTER THIS, “Houston” and “Harvey” will be synonyms for a deluge of unfathomable proportions. Floodwaters crept up to the thresholds of homes at one minute; at the next, people were fleeing, knee-deep in muddy pools, surrounded by fire ants and snakes. In all the misfortune and misery of this storm, one positive note stands out: the stories of how first responders, neighbors, strangers and just plain folks threw their all into the rescue effort.

On roads that had turned into rivers, rescuers in kayaks and fishing boats searched for victims trapped in cars and on rooftops. A television reporter saw a man stuck inside the cab of a truck and called in help. A preacher up to his waist in muddy water checked marooned cars for victims trapped inside. Neighbors grabbed neighbors and heaved them to safety.

While Texas Gov. Greg Abbott (R) declared that “the cavalry is coming” with thousands of National Guard members, 20 helicopters and 60 boats and high-water vehicles, the storm was far bigger than they could manage alone. Emergency 911 services were overwhelmed, while the National Weather Service announced: “This event is unprecedented & all impacts are unknown & beyond anything experienced.” With nothing more than their own courage, good people ventured into the rushing gullies and culverts, risking their lives to save others in the unrelenting rain. As of Monday, there were more than 2,000 people rescued and hundreds more waiting for help.

Lest anyone breathe a sigh of relief, this storm promises to upend lives for years to come. Already, 30,000 people have been forced to flee to shelters; they may not return home for some time. Rebuilding and restoring the region is going to require billions of dollars. The federal government, with help from Congress, needs to respond generously and without partisan rancor, hard as that is to imagine in today’s environment.

The storm will also raise questions that deserve answers after such a disaster. One of the most consequential is to what degree superstorms are being made even more frequent and ferocious by global climate change. Each storm is different, but Hurricane Harvey gathered strength after months in which winter temperatures in the Houston area and readings in Gulf of Mexico waters have been smashing records; last winter, the average sea surface temperature never fell below 73 degrees for the first time on record.

As temperatures rise and megastorms smash into the coasts more often, to what extent should planners and builders of modern cities prepare for once-in-a-century disruptions? Harvey, Sandy and Katrina may be remembered as the wake-up calls of our age. They must be heeded.