Virginia Railway Express says passengers should expect heat-related delays this afternoon and evening on the Fredericksburg line.

"The heat-related speed restriction delays accumulate over the course of the trip so the farther you go, the longer the delay will be," said the company in an alert.

"If your destination is Franconia/Springfield, you will likely not notice the two-minute delay. However, if you travel all the way to Fredericksburg, the delay will be approximately 11 minutes," VRE said.

With temperatures expected to climb to the middle and upper 90s—and heat index values that could reach 105—the National Weather Service has issued a heat advisory from noon to 8 p.m. Wednesday across Northern Virginia, including Fairfax County.