It’s a scorcher. As a result, Metro is taking some precautions to keep trains running. Among those:

•There will be some speed restrictions on sections of the Gold Line, Expo Line and Green Line where power zones are strained or under extreme heat. Speed restrictions are precautionary measures during extreme weather conditions to ensure we do not cause damage to the tracks or overhead catenary system, which are at the upper range of heat tolerance right now

•As a result, expect 15 to 20 minute delays on the Gold Line and minor delays on the Expo Line and Green Line. The Gold Line Foothill Extension will see the greatest impact — not surprisingly, because of the heat in the Foothill area.

•Trains may arrive several minutes behind schedule and also take longer during the ride.

•For up-to-date service advisories, follow our general Twitter stream or our Twitter stream with only service alerts.

•Also, Metrolink has heat-related restrictions in effect. From their website:

Starting at 11 a.m. today, Metrolink will have Level 2 Heat Restrictions system-wide due to the extreme temperatures. During the restrictions, passenger trains do not operate above 50 mph and slow down on the turns, which will result in delays of 10-45 minutes. These restrictions and delays are expected to continue late into the evening tonight and may be implemented again tomorrow.

Metrolink is notifying passengers in advance through social media, conductor announcements and station electronic signs so they can plan for the delays.

As information, extreme temperatures and swings in temperatures (over 30 degrees) can cause rail to expand or contract at a much higher rate than normal which could lead to a broken rail (cold temperatures) and track thermal misalignment (very hot temperatures). There are many preventative measures that are performed during construction and maintenance of track  to prevent any adverse movement of the rail. As an added precaution, during periods of extreme cold or hot weather, additional track inspections are performed and heat restrictions are imposed.