Beguiled by images of sunny Italy, a friend flew off to Rome one winter a few years back carrying only a light raincoat in case the nights proved chilly. He arrived in a snowstorm, slogged through slushy streets to his hotel and promptly came down with a bad case of sniffles that plagued him for the rest of his stay.

I had him clearly in mind when I headed for Europe for two weeks last winter on an off-season trip of my own, packing enough cold-weather gear to combat the next ice age. Happily, it turned out to be excess baggage. A warm sun caressed the Continent, and I seldom had to wear anything heavier than a sweater.

Having toured Europe during almost every month of the year, I gradually have come to the conclusion that the off-season is best -- that is, if you prefer to pursue, as I do, the Continent's historic and cultural treasures. My wife fancies gourmet dining, and that too is a satisfying winter sport.

Southern Greece, France and Italy remain mostly sunny in winter and temperatures are quite moderate. Without the searing heat of a summer day, you can explore the Palace of Knossos on the island of Crete and other classical ruins more comfortably. I've swum in the seas of Greece as early as April. Only the Alps are problematic in winter -- unless, of course, you are a skier.

On a mid-January trip to London years ago, the skies poured steadily during my entirestay. It was my first visit, but I really wasn't all that disappointed. The gray, overcast days confirmed all my expectations of London as depicted in the movies. Had the sun been shining, I might have felt I had missed the real London. If you play these little mind games, travel is more fun.

The weather obviously is a major consideration when planning a winter trip on the far side of the Atlantic. A certain self-discipline is needed to exchange the cold, dreary gray of a February morning at home for the prospect of the same thing in Frankfurt, Prague, Vienna, Brussels or London -- all stops on my most recent itinerary. A fresh snowfall can transform Europe's old capitals into fairy-tale fantasies, but the illusion disappears quickly when you must wade through the inevitable slush.

Skiers obviously would be delighted to see the Alps buried in deep snow this winter. Other travelers, however, can only hope for balmier days, prepare for the worst and then count themselves lucky, as I did, if the sun beams down so warmly that an occasional restaurant is prompted to serve lunch at its sidewalk tables.

On one mild but breezy February afternoon, I spotted several sightseers sipping coffee and nibbling rich pastries at an open-air cafe on the Grand Place, Brussels's playfully elegant old town square. If they felt a little chilled, they didn't show it. I, meanwhile, more sanely took tea by a roaring fire indoors.

Only toward the end of my trip did bad weather intrude briefly, forcing an expensive change in plans. Fierce rain squalls hit the west coast of Britain and the Continent, canceling the ferry I had intended to take across the English Channel from Brussels to London. While the storm raged, I lingered in a warm and inviting cafe, eating heaping plates of fresh mussels and frites before flying to London. Unfortunately, the air fare cost $110 more than the ferry passage -- but I had to move on.

Although Europe can't always promise gentle weather, winter has special compensations -- as many travelers are discovering. A record 3.2 million Americans visited Europe during the 1988-89 off-season, a seven-month period extending from October through April. By comparison, about 4 million Americans crossed the Atlantic during 1990's summer peak season, the five-month period from May through September. Winter is catching on.

To be sure, many of these winter travelers went abroad on business. But European tourism officials are convinced that growing numbers of American vacationers make up a large part of the flow, many of them taking advantage of the considerably lower transatlantic air fares available in winter. I paid only $336 last year for a round-trip Pan Am ticket from Washington to Frankfurt with a return flight from London. This year's off-season fares are somewhat higher -- the soaring price of oil is one reason -- but tickets right now are still up to hundreds of dollars cheaper than they were in summer.

Many winter travelers are eager to sample Europe's exciting cultural scene when the theater, opera, ballet and other performing arts are in full swing. Often there's something new. In London, we got orchestra tickets to a delightful new musical, "Noel and Gertie," about entertainers Noel Coward and Gertrude Lawrence. This winter, Copenhagen's famed Tivoli Gardens opens its gates for the first time in off-season for a series of star musical performances in the Tivoli Concert Hall.

Because of the cultural activity, European tourism promoters call the off-season the "Lively Months," and I won't quibble with them. Even tour operators specializing in the Soviet Union are promoting the Russian heartland as an exotic off-season destination.

"Is it cold in Moscow and Leningrad in the winter?" asks the Russian Travel Bureau, an American tour company in New York, and then advances this answer: "Of course it is. Wars have been lost because of the Russian winters ... . " But the cold is dry and "very bearable when one is properly dressed ... theater life is booming, crowds are few, the food most tasty {and} the vodka great for cold weather ... . "

Several European cities feature Christmas markets, where crafts workers and other vendors gather to sell holiday items. Brussels holds a medieval-style Christmas Market this winter from Dec. 7 to 9, with jugglers, musicians and magicians. And other markets are held annually at varying times in December in Vienna, Stockholm, Rome, Berlin, Munich and Nuremberg (where the event dates back to 1697). Venice celebrates Carnival this season with music and masks from Feb. 3 to 13.

In the dead of winter, you can go ice skating in Sweden and warm up in a sauna in Finland. But spring comes surprisingly quickly in Europe. In London in early March this year, the parks were full of daffodils and other blooms. And the annual tulip show at Keukenhof Gardens outside Amsterdam traditionally begins in late March.

In a way, Europe seems more European in the winter. I figure it's because the locals reclaim their cities when the summer visitors go home. You can distinguish them more readily on the streets and in museums, since their presence no longer is diluted by parades of Americans and other tourists pouring from a caravan of motor coaches.

In February, the folks around me taking in the superb collection of Bruegel paintings in Vienna's National Gallery of Art almost certainly were Viennese, or at least Austrians in town for a day from a neighboring community. On a summer visit to Vienna a few years back, I saw the same Bruegels -- or tried to catch a glimpse of them -- in the midst of what seemed to be half the population of New Jersey.

One tends to step more briskly in frosty weather, but I found the overall pace of last winter's trip to be a bit more relaxed than it might have been in summer. Maybe this is because winter days are shorter, and I could not cram too many activities into my itinerary. Several times I even was able to grab a quick nap after the museums closed and before it was time for dinner.

The huge tourist crowds endemic to summer all but disappear in the off season, and their absence is another factor reducing wear and tear on the traveler's psyche. I had last seen the Tower of London, one of Britain's major sightseeing attractions, almost a quarter of a century ago, and so I wanted to return last winter to refresh my memory. At the entrance, a weathered sign indicated that last summer's visitors could expect up to an hour's wait before admittance. At noon on March 2, a wonderfully warm and sunny Friday, I walked through the high gates of the historic castle without a moment's delay. And there was only a momentary backup to see the famed British crown jewels, protected in a subterranean vault.

Indeed, almost every aspect of European travel is easier when you are not competing with summer's throngs. You ask for a room with a view and maybe get it, show up at a fancy restaurant without reservations and are seated, exchange currency without standing in line, and enjoy the privacy -- if you seek privacy -- of an otherwise empty compartment on a train.

We booked first-class seats on the Zapadni Express from Frankfurt to Prague, which probably was a mistake since we sat alone most of the day. In a second-class car, we might have had a chance to talk to Czechoslovaks about the dramatic end of the Communist regime in their country. Our fellow passengers were in a festive mood, as we discovered when the dining car opened for lunch. They filled the tables immediately, laughing and chattering excitedly while the beer flowed freely.

I flew to Europe carrying a wool-lined raincoat, a ski hat, gloves, scarf, long underwear and rubber boots. I was prepared, although I probably could have left some of the stuff at home, even if the weather had turned awful. In Europe's cities, much of a tourist's day is spent indoors summer or winter -- in museums, historic dwellings, concert halls, restaurants and your hotel. Despite the woolens, I actually tend to travel lighter in winter. You can wear the same dark clothing for days, and it continues to look reasonably fresh.

On the down side, the prospect of bad weather is surely the major drawback to winter sightseeing, but it's not the only one.

Stripped of leaves and blossoms, the gardens that enhance many of Europe's historic buildings can only hint of their summer beauty, and the fountains are shut off.

Some offbeat attractions, such as Bruegel's mausoleum in Brussels, are closed during the off season. I am a Bruegel fan and wanted to pay my respects on my first visit to Brussels, but I couldn't because the site is open only in summer.

And those lofty European cathedrals, which are pleasingly cool in summer, turn almost frosty in mid-winter regardless of the temperature outside. If you are looking for sanctuary from a chill wind, head for a cafe instead.

In my mind, I make only one concession to winter. I like to stay in an especially nice hotel or pension. If the weather gets really nasty, I can curl up in my room for an afternoon with a good book.

Some things to consider if you are planning an off-season trip to Europe:

Air fares. At summer's end for the past two years, U.S. airlines flying the Atlantic have offered special winter air fares, good for travel from about mid-October to mid-March. Unfortunately, the deadline for purchasing most of these bargain tickets was Sept. 30. Keep an eye out for new ads in case the carriers decide to repeat the offer again later this year.

Some special European fares are still available from at least one foreign carrier, Icelandair, but only through Monday. Icelandair, which departs Baltimore-Washington International, is quoting a round-trip fare of $348 to Luxembourg, $362 to London, $404 to Paris and $488 to Copenhagen. Travel must be completed by March 7, but the fares are not valid during the Christmas holidays, Dec. 13 to 25.

Even though you may have missed out on the early-bird specials, fares to Europe from Nov. 1 through March can be several hundred dollars cheaper than during the summer peak season. Pan Am currently is quoting a round-trip fare of $492 between Washington and London, good for travel beginning Nov. 1. The ticket is nonrefundable and must be purchased 30 days in advance. Pan Am's nonrefundable fare for travel next June to London is $756.

Accommodations. Many hotels throughout Europe reduce rates from 10 to 50 percent during the off season, according to the 24-nation European Travel Commission. As in the United States, many of the best rates are on weekends in big cities when demand from business travelers is light.

Among the reductions: 20 to 30 percent off hotel rates in Belgium during January and February; up to 20 percent off in Greece in winter; up to 20 percent off in Amsterdam in winter; lower weekend rates in France and Denmark; up to 20 percent off in Portugal winter and spring; and 30 to 50 percent off in Yugoslavia from November to April.

Coming events. The winter cultural calendar, compiled by the European Travel Commission, is full. Among the big events:

Paris inaugurates the first full season of its new opera house, Opera de la Bastille, on Nov. 13 with a production of "Otello," starring Placido Domingo.

Salzburg marks the 200th anniversary of the death of Mozart with a production of his opera "The Magic Flute" as well as a series of concerts, recitals and chamber music performances, Jan. 25 to Feb. 2.

The Royal Danish Ballet in Copenhagen has scheduled three world premieres during its winter season.

The Royal Academy in London is exhibiting a large collection of paintings by Monet through Dec. 9.

Luxembourg plays host to an international exhibit of antiques and fine arts March 7 to 10.

The Danish Museum of Decorative Art in Copenhagen is featuring a centennial exhibit, "Flowers for Every Rhyme and Reason," through Dec. 2.

For a full winter calendar of events, send a stamped, self-addressed envelope (long size) to European Events, Box 1754, New York, N.Y. 10185.