Metrolinx says GO Transit and UP Express trains will be going slower Wednesday afternoon due to the warm temperatures.
The transit agency says it's issuing a temporary slow order for all GO and UP Express trains between 2 p.m. and 6 p.m., which will result in minor delays for the afternoon commute.
Train speeds will be cut by about 24 km/h, which Metrolinx says may add 10 minutes to the average trip.
Metrolinx says sustained temperatures above 30 degrees Celsius can cause what it calls "sun kinks" in steel rails.
These bends in the rail can cause a safety issue if trains pass over them too quickly.
