In an effort to shrink the federal government, President Trump and congressional Republicans have taken steps that are diluting the country’s ability to anticipate, prepare for and respond to catastrophic flooding and other extreme weather events, disaster experts say.

Staff reductions, budget cuts and other changes made by the administration since January have already created holes at the National Weather Service, which forecasts and warns of dangerous weather.

Mr. Trump’s budget proposal for the next fiscal year would close 10 laboratories run by the National Oceanic and Atmospheric Administration that research the ways a warming planet is changing weather, among other things. That work is essential to more accurately predicting life-threatening hazards. Among the shuttered labs would be one in Miami that sends teams of “hurricane hunters” to fly into storms to collect critical data. The proposed budget would also make major cuts to a federal program that uses river gauges to predict floods.

The president is also envisioning a dramatically scaled-down Federal Emergency Management Agency that would shift the costs of disaster response and recovery from the federal government to the states. The administration has already revoked $3.6 billion in grants from FEMA to hundreds of communities around the country, which were to be used to help these areas protect against hurricanes, wildfires and other catastrophes. About 10 percent of the agency’s staff members have left since January, including senior leaders with decades of experience, and another 20 percent are expected to be gone by the end of this year.

The White House and agency leaders say they are making much-needed changes to bloated bureaucracies that no longer serve the American public well.

FEMA, for one, “has been slow to respond at the federal level. It’s even been slower to get the resources to Americans in crisis,” Kristi Noem, the homeland security secretary, said last week at a meeting convened by the president to recommend changes to the agency. “That is why this entire agency needs to be eliminated as it exists today and remade into a responsive agency. We owe it to all the American people to deliver the most efficient and the most effective disaster response.”