Metro slowed its trains on all its above-ground tracks starting at 2:30 p.m. Tuesday due to the heat, less than two hours after announcing a new set of guidelines for how to run trains during hot spells in the wake of a recent derailment.

Separately, the agency said it would allow riders to drink water in the system on Wednesday, the fourth time this summer, as temperatures are expected to top 100 again. Normally, drinking is forbidden, but Metro rarely enforces it, issuing no citations for drinking anything but alcohol in June. Still, water was not allowed on Tuesday when the high temperature reached 100.