These are the lazy, languid days of summer at the White House, when the pressing concerns of government somehow seem far, far away.

Maybe it is the weather, the cool, summer breezes, like the one that blew across the South Lawn one morning as President Carter welcomed Australian Prime Minister J. Malcolm Fraser to the United States.

Whatever it is, it seems infectious. For a week or more, an air of unhurried casualness has filled the White House, so different from the frantic days of January and February.

It may be a sign that Jimmy Carter has grown relaxed and at ease in his new surroundings. The "mood" of the White House, if an institution can be said to have a mood, is supposed to reflect the President's mood. So relaxed, contented presidential aides are said to reflect a relaxed, contented President. Who knows for sure; the President, in public, just keeps smiling.

He has reason to smile, for he has been lucky. Since Jan. 20, his standing in the polls has risen and continues to hold. The world is at peace. The economy, still shaky, appears better than many expected. His relations with Congress, equally shaky, appear to be improving.

Five months after its birth, the Carter administration has yet to face its first genuine crisis. At a comparable time in his presidency, John F. Kennedy had been through the Bay of Pigs disaster.

All of these things no doubt are reflected in the attitudes of the Carter aides. They are probably working almost as hard as they did during those first hectic weeks. But they seem more relaxed about it, seem more at home in the White House, as if they have finally come to terms with "Washington," that symbol they campaigned against so long.

In the Rose Garden Wednesday morning, awaiting a bill-signing ceremony, relaxed, contented aides are everywhere: Hamilton Jordan, Jody Powell, Frank Moore, Tim Kraft, Dick Moe of the Vice President's staff.

Even Stu Eizenstat, already known as the deadly serious "grind" of the senior staff, is there, looking relaxed. So is the White House counsel, Robert Lipshuts, introducing his daughter around.

Later, many of them will stand on the staircase that overlooks the South Lawn, idly watching their President greet Fraser David Aaron of the National Security Council staff shows up for the Fraser arrival ceremony, but he kept one eye on his young son and a friend, both of them dressed in shorts, in front of him. One of them is clutching a skateboard.

It was not so long ago that these men seemed buried in paper and meeting. They were struggling to gain control of new jobs and responsibilities. There was never enough time for anything.

But now there is time to stand in the Rose Garden awaiting the President, to chitchat and banter with one another and with the reporters they are slowly growing to know. A congressional relations aide expresses satisfaction with all the recent stories saying that they are not, after all, a horde of Southern know-nothings destined to be chewed up by the sophisticates on Capitol Hill.

The President moves through a busy day of public appearances - the signing ceremony, the Fraser arrival, meetings and lunch with Fraser, a talk to the White House Fellows, more talk to the Advertising Council. He falls behind schedule, arriving late in the Rose Garden to greet the White House Fellows.

There may be hell to pay for that, for Carter insists on keeping to his schedule. Or maybe he, too, is feeling the cool summer breezes and won't care.

No matter. Waiting for him, there is time to wander to the rear of the Rose Garden, to sprawl across one of the lawn chairs there and fantasize that there is a tall, cool drink in your hand.

There are advantages for Presidents and their press secretaries in days like these. No one is in much of a mood to fight over the issues of the day, there being so many other more pleasant things to think about and do. The mood of the White House is reflected, too, in the mood of the White House press briefing room. And there, on these days, the atmosphere alternates from summer languor to the giddiness of a fraternity beer bust.

So it was that one of Jody Powell's news briefings this week lasted less than five minutes, probably a White House record if such records are kept. He had one brief announcement; reporters had a couple of uninterested questions about James Earl Ray and that was it.

On Wednesday, the briefing lasted longer, almost 30 minutes. It was all in good fun. True, someone was shouting questions about how Carter could say we were maintaining a military balance in Korea while we are withdrawing troops from the area. But Powell, as he so often does, fending them off with a wisecrack, recalling how a brave band of Southern boys whipped a Yankee army twice its size at Chancellorsville.

Later, someone says that Powell is getting away with murder, and everybody agrees. His country boy humor and quick wit are no substitutes for answers.

But there is always tomorrow. Tomorrow, maybe it will turn cold and rain, driving the people out of the parks and into their offices. Tomorrow there will be plenty of time for hard questions and serious answers about promises made, promises kept, promises broken.