Once a year, major league baseball comes back to Washington. Yesterday was the day.

The Minnesota Twins, fresh from their seven-game World Series victory over the St. Louis Cardinals, returned to the city where they once played as the Senators for a quiet, traditional reception at the White House and a boisterous rally on Capitol Hill.

Activities that were subdued to the point of solemnity at the White House turned raucous in the afternoon as the Twins and hundreds of their local rooters converted a Capitol Hill caucus room into a miniature Thunderdome.

At an 11:30 a.m. Rose Garden reception for the team, the Twins brought President Reagan all the appropriate mementos, including a bit of the intense noise of the Hubert H. Humphrey Metrodome. Twins Manager Tom Kelly was in charge of the decibels, presenting Reagan a whistle on behalf of the Twins' wives. "If you need it to referee any of your talks coming up," he said, "just whip that baby out."

Reagan took the whistle and used it to end the brief ceremony. But not before inviting the Twins to return permanently. "If you guys ever get tired of playing in front of those screaming, adoring fans," he said, "you're welcome back."

With much of the Minnesota congressional delegation looking on, the Twins gave Reagan two Kent Hrbek bats they had autographed and a Twins pinstripe jersey with "Gipper" and the number 1 on the back.

From there, the team went to Capitol Hill for an invitation-only lunch set up by the Minnesota delegation. And then it was show time with Rep. Martin Sabo (D-Minn.). The morning and lunchtime festivities had been a bit tame, he said. Now it was rally time.

Out came a cache of some 500 Homer Hankies for the turnaway crowd of 600, the Twins' symbol that turns the Metrodome into a sea of white. Twins fans in Minnesota had waited in line up to 2 1/2 hours to buy them at 50 cents apiece. Yesterday, some members of the congressional delegation wore them neatly folded in their coat pockets -- the latest Minnesota-chic fashion statement.