6:20 p.m. Update: Penn Line 640 is 10 minutes late approaching BWI; Camden Line 852 is 10 minutes late approaching Muirkirk.

6:10 p.m. Update: The Maryland Transit Administration is reporting delays across all three lines due to heat restrictions and congestion.

Penn Line trains 436 and 634 are running 20 to 30 minutes late; Brunswick 877 and 893 are running 10 minutes late. Camden Line 850 is operating 20 minutes late.

5:05 p.m. Update: MARC 873 is running 15 minutes late. MARC 891 is operating 12 to 15 minutes late.

5:03 p.m. Update:Camden Line Trains 846 and 848 are running 10 to 15 minutes late due to heat restrictions.

4:42 p.m. Update: The Maryland Transit Administration reports that several trains are running late due to today’s heat restrictions. Train 875 on the Brunswick Line was reported 5 to 10 minutes late; Train 891 on the Brunswick Line was reported 10 minutes late; Train 853 on the Camden Line was reported 25 minutes late.

Original post: Monday’s summer-like weather has prompted CSX to issue heat restrictions for trains traveling on the Maryland Area Regional Commuter Brunswick and Camden lines.

CSX operates the Brunswick and Camden lines on CSX-owned tracks. The Brunswick Line carries passengers between Washington and points north and west, including Frederick and Martinsburg, W.Va. The Camden Line connects Washington and Baltimore.

The heat restrictions are in effect until 7 p.m. and means trains will operate at 20 mph less than normal speeds, to a minimum of 40 miles per hour. The Maryland Transit Administration estimates that delays will range from 10 to 15 minutes.