Boston — If the stormy California weather has proved a royal disappointment during Her Britannic Majesty's 10-day visit, perhaps she should try Boston. Here, after all, the winter weather is insured by a firm Queen Elizabeth II understands: Lloyd's of London.
Boston, of course, is not King Arthur's Camelot - where, according to the popular musical, ''the winter is forbidden 'til December, and exits March the 2 nd on the dot.''
Here it can freeze up in October, be buffeted by blizzards in May, or (as in this year, one of the warmest winters on record) it can soar into the 70s in January.
But so strong is New England's snowbound reputation, say officials of the Greater Boston Convention and Tourist Bureau, that a number of conventions are reluctant to meet here during the winter for fear that a storm or two could spoil their plans.
So the convention bureau has studied weather records from the past 30 years. As a result, they're convinced that the winters here are quite acceptable - so convinced, in fact, that they have arranged to have Lloyd's insure conventions against weather-related losses.
The coverage, which ranges up to $5 million per meeting, will be paid for by local businesses - an offer which, says bureau spokesman Gary Grimmer, no other American city can at present match.
Nor is the bureau the only Boston customer to use Lloyd's this way. The Massachusetts Horticultural Society has taken out Lloyd's coverage to protect against financial losses at its flower show this month.
Several years ago, similar ''convention cancellation policies'' also reimbursed a meeting scheduled for the Hyatt-Regency Hotel in Kansas City the day after its walkway collapsed and a Miami Beach group tangled up by the air traffic controllers' strike.
So far, convention-planners gathered under the umbrella of the American Society of Association Executives (ASAE) are modestly impressed by the convention bureau's plan.
''It's a gimmick,'' says ASAE president R. William Taylor, ''but at the same time it's a clever gimmick.'' The insurance policy itself, he adds, is not as important in luring conventions as the fact that ''they've made their point that the city does not close down.''
''Let the word go out,'' says Boston's convention bureau president Robert E. Cumings, that ''Boston is warmer in winter than Reno and many other Northern cities, has less snow than Chicago, has fewer rainy days than Miami, and less airport closings than Los Angeles.''
Weather, however, is not the only problem hampering the city's efforts to become a major location for conventions. The city also lacks a first-class convention facility to compete with such nearby cities as New York (now spending center is now open).
All Boston can offer is its aging Hynes Auditorium. Recently purchased from the city by the state, it is scheduled for a $100 million rehabilitation that will double its size.
The new Hynes, however, won't be completed until 1987. In the meantime, Boston's hotel market is booming - adding some 5,000 new hotel rooms between 1981 and 1984, on its way toward a total of 12,705 by early 1985.
What becomes of all those rooms if the large conventions don't come to Boston? So sobering is that question that the convention bureau is offering the Hynes rent-free for major conventions planning to meet between Nov. 15 and March 31. Will the conventions come in the winter? Yes, says Mr. Taylor - since ''everybody can't meet in April and October,'' he says.