The Maryland Transit Administration says it is taking steps to protect MARC trains, equipment and passengers during the heat wave.
The MTA says the severe heat, forecast through Saturday, pushes equipment to the limit. The agency says it will aggressively address the issues when they occur and resolve them as quickly as possible.
Water coolers will be provided at Union Station in Washington.
In June 2010, hundreds of passengers were stranded for two hours on a broken-down MARC. Several were treated for heat-related issues.