[This post has been updated.]

It’s come to this: The heat is so intense that Metro has suspended its no-drinking policy, at least for water. Riders can bring water into the transit system and consume it on buses and trains and in stations Wednesday and Thursday.

(Jahi Chikwendiu/The Washington Post)

Some Metro riders are bound to encounter hot cars during this heat wave. But there are things, besides staying hydrated, that you can do to help yourself and your fellow riders.

These are some of the tips I’ve collected over long, hot summers.

* If the Metro car is hot, don’t just sit there. At the next station, try another car. The cars have their own cooling equipment. On summer days when I’ve carried a digital thermometer from car to car, I’ve found variations of 10 degrees.

* Riders can usually tell the difference between a car that’s warm because it’s hot outside and a car with an AC problem. I’ve seen riders on platforms pivot away from a car entrance as soon as the doors open, and they feel the air from inside. Also, the car probably won’t have too many riders aboard, because they’ve already followed step one and moved.

* Go to one of the rail car intercoms and tell the operator the car is hot. The operator will call that in. Metro has maintenance staffers along the lines so they can board the cars and try to fix the problems. A hot car is a sufficient emergency to use the intercom. Riders also can call in the information about heat problems to Metro’s customer service phone, 202-637-1328. Remember the car number.

* If a train car’s doors don’t open when it reaches the platform, it may well be that maintenance couldn’t fix the problem on the go and sealed off the hot car.

* The age of the rail car isn’t a good predictor of the AC quality. The 1000 series cars, the oldest and most numerous ones in the fleet, have gone through a mid-life rehab. Complaints have been more frequent about the newer 5000 series cars. I’ve rarely encountered a temperature problem in the newest cars, the 6000 series.

* Above ground, the sunlight shining on one side or the other of a train makes a big difference in the temperature.

* The rail cars are never going to feel like the inside of your home or office with the AC on. There are three doorways on each side of the car to suck in hot air and release the cool. Trains that have recently entered service tend to be warmer, because the air conditioning hasn’t had a chance to take effect.

* In the stations, the wide open entrances, the presence of hundreds of passengers and the trains pushing warm air ahead of them all contribute to the heat.

* The last underground station before the line goes above ground can be just ghastly. That’s true at Union Station and at Ballston, for example.

* Temperatures within the stations also vary. Move around. In one of the portal stations, like Union Station, it may be slightly cooler on the side farthest from the outside air. During the summer, Metro puts big fans on some hot platforms. It can help.

* On any of our rail systems — MARC, VRE or Metrorail — the line operators may order the trains to slow down for safety, because heat kinks can develop in the rails.