If temperatures top 100 degrees Wednesday, Metro may impose heat restrictions on trains again, making normals commutes slower than usual.
The National Weather Service has issued a heat advisory that takes effect at 11 a.m. for the entire Washington region as forecasters say it could feel like 109 degrees outside.
Metro slowed all trains down to a 35 mph maximum speed on above ground tracks Tuesday, leading to delays and long waits.
"It's a much more crowded platform than I have ever really seen before," said Richard Cheuvemann, Virginia resident.
As of 7 p.m. Tuesday, the restrictions have been lifted.
Metro officials say the decision to slow down the trains is based on several criteria, including the actual temperature of the rail.
Transit officials say direct sunlight can cause rail temperatures to reach 135 degrees or higher, which could lead to safety problems.
"I'd rather be late than derailed on the side and really sweating," said Berry Freeman, Virginia resident.
While water bottles are allowed on buses and trains on hot days, cold air conditioning may not be guaranteed.
"It's hot outside. It's hot on the train. You pay your money. You want to be comfortable," said Johnnie McCain, Maryland resident.
"While these speed restrictions may cause some delays and inconvenience, they are intended to put the safety of our passengers first," said Dave Kubicek, Metro's Deputy General Manager for Operations.
On July 6, three cars of a Green Line train bound for Hyattsville derailed when it tried to run through a section of track warped by the triple-digit temperatures.