With better sewage systems, smaller networks, and deeper tunnels, major cities throughout America say heavy rain rarely, if ever, leads to subway closures.

Even in London, which boasts the world’s oldest subway, weather-related suspensions are extremely rare, according to a spokeswoman for the London Underground, as heavy rainfall is swallowed up without need for service interruptions. When faced with days of torrential rain earlier this month, the system closed down sections of two lines for part of one day, the spokeswoman said. Transit officials in Boston, Washington, D.C., San Francisco, Los Angeles, and Philadelphia all said they could not recall a time within the past year in which subway service needed to be suspended because of weather.

“If you’re talking about the subway, there aren’t any weather-related situations that would cause us to shut it down,” a spokesman for the Los Angeles Metro, Dave Sotero, said.

Experts point to several challenges faced by the New York City subway system, most notably its geography: The system is encircled by bodies of water, and many of the tunnels are below sea level. “There are a few low points in this system that can act as nodes that can disable a large part of the system,” a professor at New York University’s Wagner Graduate School of Public Service, Rae Zimmerman, said.

Many of the nation’s subways are newer than New York’s and better engineered to deal with flooding, Ms. Zimmerman said.

Many other cities have tunnels that are deeper than those of New York, she added, which tend to take in less rainwater.

“A lot of the tunnels are right near the surface of the street, and the tunnels act as a conduit, whether you like it or not, for water,” Ms. Zimmerman said.