Washington in July is not exactly April in Paris, but apparently not everyone scrambles to the Vineyard or the Hamptons when a gust of humidity descends over the cocktail hour.

An impressive coterie of society and the political community was entertained by Italian Ambassador Rinaldo Petrignani and his wife, Anne, last night at a sparkling black-tie dinner to honor Sen. Paul Laxalt (R-Nev.) and his wife, Carol. As with most Washington black-tie dinners where a powerful political person is honored, there was no particular reason for the party.

Unless of course, you count the fact that Laxalt is often referred to as one of President Reagan's closest friends and that Carol Laxalt is of Italian descent.

"I have no illusion as to why I am here tonight," joked the senator. "My Italian connection. Were I not married to Carol Bernardini I doubt whether this event would have occurred."

Despite the fact that at least 54 of the powerful were still in Washington in the middle of the heat wave, most of the cocktail conversation centered around how people were going to get out of Washington--from Egyptian Ambassador Ashraf Ghorbal's upcoming trip to Alexandria, Egypt, to Sen. Patrick Leahy's (D-Vt.) vacation on his Vermont farm.

And take Attorney General William French Smith. Next weekend he'll be heading out to Monte Rio, Calif., for the annual private meeting of the all-male Bohemian Club, a 2,000-member, exclusive retreat.

"You bet," said Smith, when asked if he was going to the vacation spot. He was less precise on what exactly he will be doing there. "Well, there's no way to describe it. You have to experience it," said the attorney general. "There is a law that no business goes on out there. I play tennis and golf, but that's not what I do there. . . . You have to experience it. I can't even explain it to my wife."

"No. Bill doesn't belong," said Drue Webster, wife of FBI Director William Webster. "But he's going next weekend to find out what the big boys do at camp."

"It's really no big deal," explained Interstate Commerce Commission chairman Reese Taylor, who has attended the retreat in the past. "It's a lot of entertainment . . . entertainers belong. . . . And a lot of talking going on between the men . . . you know, 'How great I am' and all that."

Early thundershowers kept the party inside the peach-and-cream-colored drawing room, instead of on the sprawling grounds of Firenze House, the ambassador's residence on Albermarle Street NW, which is the old Guggenheim estate. The room rumbled with political chatter and loud laughter, as rounds of cocktails were circulated among the guests.

The first course for dinnner was ravioli nudi, or nude ravioli. This did not look like traditional white ravioli stuffed with meat. It was green.

"I guest that part of the ravioli concept is that if it is white it is very well-dressed," smiled Pier Luigi Rachele, political counselor to the embassy.

After the ravioli, Petrignani toasted the absent President Reagan and everybody stood up for a moment. Then everyone sat again for shrimp salad, roast veal and spumoni. Among the other guests were French Ambassador Bernard Vernier-Palliez, Secretary of Energy James Edwards and his wife, Ann, Ambassador-at-Large Daniel Terra, White House personnel director Helene von Damm, public relations czar Robert Keith Gray, David and Susan Brinkley, Bendix Vice President Nancy Clark Reynolds and Sen. Robert Dole (R-Kan.) and presidential assistant Elizabeth Dole.

In his toast to Laxalt, Petrignani called the senator a "man who matches the mountains of his native state" and called him a "prominent political person on the Washington scene." Laxalt thanked his hosts and said, "This country would be hard pressed to find a more loyal or staunch ally than we have in Italy."

After gulps of champagne and a few more mouthfuls of peach spumoni, the crowd got down to some serious business: large and small cigars, Courvoisier, and talk about forthcoming lunches, babies and of course, where everyone hoped to be in August.