Summer in Washington means Seersucker Thursdays in the Capitol.

The longstanding tradition started as a way to keep cool in the D.C. swamp in the summer but has turned into a time for bipartisanship and camaraderie.

Louisiana Sen. Bill Cassidy has been looking forward to National Seersucker Day and is once again teaming up with Sen. Dianne Feinstein to lead the celebration.

[Seersucker, Seersucker Everywhere]

“National Seersucker day is a just plain fun and celebrates an American product invented in my home state of Louisiana,” Cassidy said. “It’s a lighthearted tradition and shows that the Senate isn’t a bunch of boring suits.”

The senator has a seersucker suit that he will wear to work on Thursday.

He also encouraged his fellow senators, including new Louisiana colleague Sen. John Kennedy, to get in the spirit.

“I reached out to all of my colleagues and invited them to participate,” Cassidy said. “Why wouldn’t you? It’s fun.”

Staffers and other Capitol Hill employees are also often spotted wearing seersucker on Thursdays in the summer.

Cassidy reintroduced National Seersucker Day to the Senate in 2014 after it was discontinued in 2012. The tradition was started in 1996 by former Mississippi Sen. Trent Lott.  

[The Political Stripe]

The air-conditioning that keeps the Capitol’s halls and rooms cool did not get installed until the 1950s.  So, Lott decided the day would take place when it got warm in the second or third week of June.

In 2004, Feinstein encouraged fellow female politicians to participate in the day and the next year she gave several women in the Senate outfits to wear.

It’s still a relatively cool start to the summer in Washington. Thursday’s temperature is supposed to reach only the low 70s.