It's said of other places but often holds true for London: if you don't like the weather, wait a minute. Many visitors ask 'what will the weather be like in...?' but the best and most honest answer is that we won't know until that time comes.
But there are a few basics that may help in considering when to travel to London.
Winter. Even the word sounds chilly, but days in London aren't always cold and grey, although they can be. There can be drizzle and showers but pale sunshine as well, just not a lot of it. And that lack of sunshine is what may make people think that London in winter is undesirable, as the days are short which means less time for sightseeing as well as less sunshine. The options at www.timeanddate.com will allow visitors to check sunrise and sunset times for dates throughout the year; it's a good planning tool.
Will there be snow in London in winter? Yes there may be, and there may be enough to settle on streets and pavements in the city centre as well as at airports and on railway lines. No two winters are alike but if travelling in December and January be prepared for snow and perhaps a few icy patches on some pavements. Although the days will be lengthening from January there is always the potential for clear, cold and windy days, perhaps with a bit of snow, through the end of February and to early March.
Spring will come though, as it always does. Even if the weather stays resolutely cool, by early March there will be buds on trees and the first stirrings of change. The longer days usually mean more sunshine, but February and March can be damp, moreso than the winter months.
Summer isn't just for Pimm's, Wimbledon and barbeques, it should be the high point of the year. Very long days mean more sunshine, and that often sees Londoners move out of doors en masse, whether to pavement cafes, deck chairs in Hyde Park or to the seaside. Although long (three to four weeks or more) stretches of sunny and clear days aren't the norm there can be days when the temperatures will rise about 25 - 28C; central London can feel very warm on days like those. Sunscreen will be needed, especially for those who take river cruises on the Thames!
But summer fades and Autumn will follow. September can be a very pleasant month, with mild days and clear but cool nights with the first snap what's to come in the air. October can also be mild and sunny, a last gasp of what was, but by the end of that month and with the clocks going back the move to winter will be felt.
If you think that a word has been missing, you're right. Rain. England's maritime climate means that rain could fall at any time - and it does - but day upon day of rain and grey skies aren't common in London. But again, expect the unexpected: the sky could darken and rain could pelt down in buckets for five or ten minutes then the sun come out.
So let's look at a month by month When To Go scenario, always bearing in mind that it's subject to change. There are a few general hints and tips below as well.
January - the weather will still be wintry, with grey skies and always a possibility of rain or snow. January has a bad press for after-holiday blues, that 'oh no, back to work!' feeling, and on the whole it's not a month when a great many visitors make their way to London.
February - the days will be lengthening noticeably. Winter will still be in situ, but the sight of crocus and daffodil shoots in parks and gardens may boost one's spirits. Temperatures should be warmer than in January and it may be windy at times.
March - change in the air. By mid-month there should be signs of Spring, although snow has fallen in London in March. Clear days and cool evenings with more sunshine bring increased numbers of visitors.
April - not much change from March except that Spring should be more firmly entrenched.
May - a very nice time to visit London. Longer days and most sights and attractions aren't as crowded as in Summer. But having said that, with two Bank Holidays in May many Londoners and others from the UK will be on the move, all seeking to enjoy a bit of a break.
June and July - should be the high point of the year. Long days that may be warm to hot - daytime highs of 30C aren't common but do happen - and mild nights mean people from all over the world will make their way to the capital. Take advantage of Summer for a wander along the South Bank or a visit to a park or riverside pub. This is the time of year when day trips outside of London may be a nice plus to a city-based visit.
August - family holiday time. Schools will have let out, and although the days will be shorter there will still be plenty of visitors making their way to London.
September - second best time to May for many visitors to the city.
October - time for a change. There usually aren't a great many visitors to London during this month but business people will keep the hotels occupied. The gardens and parks of London will be attractive in a way different from Summer; even the Tower looks a bit different as the days start to draw in.
November - to stave off the dark nights, this is when Londoners start to get ready for the Christmas holidays. The lights along Oxford and Regent Streets are usually lit in the first or second week of the month, with substantial ceremonies to do so. One of the best ways to see the lights is to sit upstairs on a double decker bus that travels the length of those streets to enjoy the views not only of the lights but of the crowds below.
December - time to celebrate. Shoppers will be out in force but it's also a time for parties, celebrations with family and friends and everything that goes with those celebrations.
Some basic information that might help deciding when to visit. UK schools' half term times are usually in February and October, with Summer holidays in July and August. Bank holidays along with school half term times may see an increased number of visitors to London along with higher than usual numbers of people on the roads, booking trains and at airports.
London's Underground is a massive system that carries millions of passengers a day. What may be unexpected for some visitors is that it can be hot on Tube trains and in stations at any time of year, not just summer. Those Tube trains will be crowded at morning and evening peak hours so be prepared not only to share the limited space but to feel warm whilst doing so.
And in opposition to this is the question of air conditioning. It's not as ubiquitous as elsewhere in the world, especially in London hotels. But many of those hotels offer fans in guest rooms, and with windows that open a bit of cross ventilation is nice on warm days. The London Overground has air conditioned train carriages; Tube trains are a work in progress.
Whenever you decide to visit London, please do so with the idea of having as good a time in the capital as you can. There's not much that can be done about the weather (except have a moan every now and then) or about crowds, but a bit of preparation will help. If it rains and you weren't expecting it then pop inside a shop or cafe for a cup of tea. If there are delays on the Underground then consider taking the bus to your next destination. Walking is also a good option - central London is surprisingly centralised - and "Boris Bikes" abound now, allowing you to rent this eco-friendly form of transport.