The cities that are better in winter
Some places are diminished by cold and some are completed by it. Knowing which is which is worth more than a good forecast.
The default assumption is that summer is when you travel and winter is when you don't. For a lot of destinations that's correct. For a specific and useful set of cities, it's backwards.
What makes a city better cold
Three things, roughly.
The life is indoors anyway. Cities whose main attractions are museums, galleries, concert halls, cafés, bathhouses and food are not diminished by weather, because you were going to be inside. Winter removes the queues and adds nothing you'll miss.
The architecture reads better without foliage. Cities built around dense stone and ornament are often clearer in winter — bare trees expose facades and sightlines that summer leaves hide.
The place has a genuine cold-weather culture. This is the strongest signal. Where cold is normal rather than exceptional, the city has organised itself around it: heated interiors, warming food, thermal bathing, seasonal markets, long evenings designed to be spent somewhere warm. You're not enduring the season, you're participating in it.
Cities that fail the test are the ones whose appeal is outdoor and seasonal — beach cities, places whose life happens on terraces, anywhere the main attraction is a garden.
What you get
Room. The most-photographed places in Europe in February are recognisably the same places, minus the crowd. The difference in an interior — a cathedral, a gallery — is dramatic.
Light. Winter sun sits low all day, which is flattering to buildings for far longer than the brief golden hour you get in summer. Photographers know this; most visitors don't.
Price and availability. Except around the specific holiday peaks, winter is when city accommodation is cheapest and most available.
Atmosphere that summer can't produce. Fog, snow, early dark, lit windows. Some cities are simply more themselves under those conditions.
What you give up
Daylight hours. This is the real cost and it's larger than people expect, especially at higher latitudes. A winter day in a northern city can give you a short usable window of daylight, which changes how much you can fit in.
Plan for it: outdoor things early, interiors for the afternoon, and accept that the evening starts at four.
Some things shut. Seasonal restaurants, rooftop venues, outdoor sites on reduced hours. Less of an issue in a large city than a small resort, but worth checking for anything specific you're going for.
Weather can be genuinely unpleasant rather than merely uncertain. Cold rain and wind is worse than cold and clear by a wide margin, and no amount of atmosphere compensates.
The holiday-season exception
There's a period around late December when winter city travel stops being cheap and quiet and becomes expensive and packed — markets, lights, and a lot of other people with the same idea.
That's a different trip, and a good one, but it isn't the quiet-winter-city trip. If quiet is what you're after, the weeks in the new year are where it lives: same cold, same low light, none of the crowd, and prices at their annual floor.
Where this fits with leave
Winter city breaks are the most efficient use of a small amount of leave in the calendar. Short flights, two or three days, low cost, and — critically — a period when almost nobody at work is competing for the same days off.
If you're rationing annual leave across a year, this is where the cheap days are. Two days in February buys a four-day trip to a city that is, for the right destination, at its best.