In Washington, the subway system, which opened in 1976, has revised its operating procedures. Authorities will now watch the rail temperature and order trains to slow down if it gets too hot. When railroads install tracks in cold weather, they heat the metal to a “neutral” temperature so it reaches a moderate length, and will withstand the shrinkage and growth typical for that climate. But if the heat historically seen in the South becomes normal farther north, the rails will be too long for that weather, and will have an increased tendency to kink. So railroad officials say they will begin to undertake much more frequent inspection.

Some utilities are re-examining long-held views on the economics of protecting against the weather. Pepco, the utility serving the area around Washington, has repeatedly studied the idea of burying more power lines, and the company and its regulators have always decided that the cost outweighed the benefit. But the company has had five storms in the last two and a half years for which recovery took at least five days, and after the derecho last month, the consensus has changed. Both the District of Columbia and Montgomery County, Md., have held hearings to discuss the option — though in the District alone, the cost would be $1.1 billion to $5.8 billion, depending on how many of the power lines were put underground.

Even without storms, heat waves are changing the pattern of electricity use, raising peak demand higher than ever. That implies the need for new investment in generating stations, transmission lines and local distribution lines that will be used at full capacity for only a few hundred hours a year. “We build the system for the 10 percent of the time we need it,” said Mark Gabriel, a senior vice president of Black & Veatch, an engineering firm. And that 10 percent is “getting more extreme.”

Even as the effects of weather extremes become more evident, precisely how to react is still largely an open question, said David Behar, the climate program director for the San Francisco Public Utilities Commission. “We’re living in an era of assessment, not yet in an area of adaptation,” he said.

He says that violent storms and forest fires can be expected to affect water quality and water use: runoff from major storms and falling ash could temporarily shut down reservoirs. Deciding how to address such issues is the work of groups like the Water Utility Climate Alliance, of which he is a member. “In some ways, the science is still catching up with the need of water managers for high-quality projection,” he said.

Some needs are already known. San Francisco will spend as much as $40 million to modify discharge pipes for treated wastewater to prevent bay water from flowing back into the system.

Even when state and local officials know what they want to do, they say they do not always get the cooperation they would like from the federal government. Many agencies have officially expressed a commitment to plan for climate change, but sometimes the results on the ground can be frustrating, said Ms. Minter of Vermont. For instance, she said, Vermont officials want to replace the old culverts with bigger ones. “We think it’s an opportunity to build back in a more robust way,” she said. But the Federal Emergency Management Agency wants to reuse the old culverts that washed out, or replace them with similar ones, she said.

Ms. Arroyo of Georgetown said the federal government must do more. “They are not acknowledging that the future will look different from the past,” she said, “and so we keep putting people and infrastructure in harm’s way.”