The Queen's visit -- warmth amid downpours

California's messy and at times destructive weather of the past several days has neither ruffled the aplomb nor dampened the good humor of the state's royal visitors - Queen Elizabeth II of Great Britain and her consort, Prince Philip.

The royal couple have seen little of California's sun and Californians have not seen as much of them as they might have in better weather. But the visit, which started Feb. 26 in San Diego and will end when they fly from San Francisco to British Columbia March 6, has so far been an apparent success despite several last-minute changes necessitated by weather conditions.

The Queen's hats have been a definite asset, both from the sartorial and celebrity-watching points of view. Many in the crowds who have stretched their necks for a peek at the Queen have at least been able to say, ''I didn't see much of her, but I did see her hat.'' As for her wardrobe, which at times has been characterized as less than trendy, she appears to have brought the right things along on this trip - from dazzling jewels and evening dresses to storm coat and boots.

Well-traveled as they are - the Queen has compiled something like 750,000 miles around the globe during her reign and Prince Philip perhaps more - the royal couple has demonstrated a knack for turning adversity or inconvenience to advantage. Their plan to steam into San Francisco Bay Thursday aboard the royal yacht Britannia was upset by stormy seas. But when he found they would instead be flying here Wednesday afternoon, Prince Philip grabbed the opportunity to schedule a rare event. He had dinner reservations made at Trader Vic's, a famous restaurant near the St. Francis Hotel, where the royal visitors have occupied the Presidential Suite.

Dining in public is something the Queen never does in England, and the Prince had remarked earlier that his efforts to ''dine out'' in other countries have usually been thwarted by security requirements. In San Francisco, the royal couple, with Mrs. Reagan and a few members of the official retinue, were able to dine ''in public'' - though they were served in a section of the restaurant not accessible to other patrons.

And what of those who came to jeer rather than cheer? Few protesters were in evidence when the Queen made appearances in San Diego, Los Angeles, and Santa Barbara. In San Francisco, a coalition of some 140 activist groups staged demonstrations in the Civic Center area and in Golden Gate Park, where events on the Queen's schedule took place. Backers of Independence for Northern Ireland were among the demonstrators, but most were protesting Reagan foreign and domestic policies.

Queen Elizabeth does not grant interviews or hold press conferences, and she seldom makes official statements outside of formal settings, but she made an exception on this visit. Standing in the rain on the steps of City Hall in Los Angeles and reading from a prepared text, she said: ''We in Britain were called upon last year to defend the principle of self-determination in the Falkland Islands. The support of your government and the American people touched us deeply and demonstrated to the world that our close relationship is based on our shared commitment to the same values.''

As an unfamiliar sun broke through scattering clouds Thursday morning in San Francisco, it appeared that at least part of her trip - including two days of festivities here and two days in Yosemite National Park, which the Queen is said to be especially looking forward to - might be accompanied by more sunbeams than raindrops.

But to millions of Californians, the central image of this historic visit has already been formed: a shortish, middle-aged woman in unpretentious rain garb, surrounded by protocol and security, stared at and cheered by drenched thousands , walking through it all with a smile, a wave, a quiet word of greeting.

''She's lovely,'' they comment. Or, ''He's a real trooper.'' It's their way, perhaps, of saying she is a fit representative of the mother country whose monarchy Americans rejected, but whose kinship and friendship have been anchors through peace and war.