Metro General Manager Richard Sarles announced today that Metrorail will add 10 cars to its rush-hour service in time for the start of the Cherry Blossom Festival, and he said they won’t go away after the blossoms have faded.

The 10 extra cars will be used on the Orange and Red lines starting Monday, he said. Five six-car trains will be converted to eight-car trains. This will add 640 seats for rush-hour riders on the lines that carry the most passengers. The transit has not special-ordered new rail cars to do this. Sarles said that extra cars are a product of a service improvement program focused on getting equipment into and out of the rail yards faster.

The annual festival, scheduled this year from March 27 through April 6, always stresses Metro’s equipment, as well as its riders, who for two weeks include a surge of tourists from around the world. Many of the busiest days in the rail system’s 35 years have occurred during recent festivals.

While Metro would love it if the tourists confined their travels to off-peak hours, they also jam their way aboard the already packed trains during the morning and afternoon rush. The regulars know the tourists: They’re the ones who’s eyes get really big when they realize the train doors aren’t going to bounce open just because they have their hands stuck between them.

Metrorail cars — as well as their riders — are under extreme stress during the festivals. Doors break down, operators unload the cars and take them out of service, and an even greater crowd builds up on the platforms waiting to see if anyone can squeeze aboard the next train.

The extra cars will help, but the trains will still be unusually crowded. The transit authority will suspend its weekend maintenance program during the festival, so riders won’t face any scheduled slowdowns caused by trains sharing tracks around work zones. Escalator and elevator repairs will continue.

Riders may catch a break as the temperatures rise on these crowded cars: Sarles also announced that Metro has been working on a more aggressive program to repair and maintain the train air conditioners, a source of many complaints during the very hot summer of 2010.

The goal of the campaign, called “Operation Cool Breeze” and begun in February, is to inspect and overhaul the more than 1,000 cars in the rail fleet.

That includes cleaning the condensers under the cars and the pipes, pans and filters over the riders’ heads, said Damon Cannon, Metro’s general superintendent of rail car maintenance, who led reporters on a tour of cars under repair at the New Carrollton yard. The intensified campaign of preventive maintenance and repair on the air conditioners will continue through the summer, he said.

When the temperatures reach the 68 to 72 degree range, Cannon said, riders should start to feel the effects of “Cool Breeze” inside the cars.