Why we won't give you a London laundry forecast
Greater London covers 607 square miles (1,572 square km).1 If you search for a laundry drying forecast for "London," many apps will give you one. DryTime won't; here is why that is a win for you.
Cut the waffle, just give me the forecast
One forecast, nine million people
A city-level laundry forecast is a single number stretched across an area the size of a small country. The weather in Hackney and the weather in Richmond are not the same weather. On a calm, clear night, the temperature difference between the dense urban core of London and its outer suburbs can exceed 8°C (14°F).2 That is not a margin of error, that can be the difference between washing that dries and washing that stays damp until you give up and put the tumble dryer on.
This is not a quirk of London. It applies to any city. Manchester, Birmingham, Bristol, Glasgow, Sydney, Dublin: all of them contain a patchwork of local climates inside their borders. A single city-wide number flattens all of that into something that sounds useful but isn't.
Why cities generate their own weather
Cities absorb heat during the day and release it slowly at night. Roads, rooftops, and concrete store warmth that open countryside sheds quickly. This is called the Urban Heat Island effect, and it is well-documented.3 The practical result is that urban areas stay warmer and drier-feeling than surrounding land, but unevenly: the effect is strongest in the dense core and fades toward the edges.
Wind is stranger still. Streets act as canyons or funnels, accelerating airflow in some directions and creating near-dead-calm pockets in others. Wind speed and direction can change significantly over distances of just a few metres in urban environments, depending on building height, street orientation, and local surface texture.4 A garden sheltered behind a Victorian terrace may sit in almost still air. A garden three streets over catches a useful westerly. A forecast that treats the city as one weather point cannot see any of this.
Rainfall is uneven too. Because of prevailing southwesterly winds and the topography of the North Downs, parts of East London receive up to 100mm less rainfall per year than parts of West London.5 Same city. Different weather. Same inaccurate forecast applied to both.
The reason city forecasts exist
City-level search queries drive website traffic. "Laundry drying forecast London" is a real search people make. Answering it with a city-wide forecast is the path of least resistance. It satisfies the search engine. It does not necessarily help the person with wet washing.
There is also a structural problem in how weather data is gathered. Standard meteorological monitoring stations are typically sited at airports or open parks. Those locations are chosen for operational reasons that have nothing to do with residential gardens.6 Thus the data that feeds a city forecast is already abstracted from the places where people actually hang washing out.
DryTime primarily uses Open-Meteo, which selects the most suitable forecast model for each specific location. From that we combine six variables: temperature, windspeed, humidity, precipitation, solar radiation, and air pressure. All calculated for your postcode, your street, your neighbourhood, not your city. The distinction matters because drying laundry is a local problem.
The physics that city forecasts miss
Drying laundry comes down to something called Vapour Pressure Deficit: the gap between how much moisture the air could hold and how much it actually holds. When that gap is wide, evaporation is fast. When it is narrow, your washing can just hang there getting smelly.
In a sheltered urban garden enclosed by buildings, the air can become saturated while a city-wide humidity reading suggests comfortable drying conditions across town. The official figure is accurate for somewhere in the city. It may not be accurate for your washing line, your garden, your street.
This is why giving you a London forecast would be doing you a disservice. A confident number based on insufficient local data is not accuracy. It is precision theatre.
What to do instead
Head over to the London map, find your corner of it, drop a pin and let us do the rest, properly.
Or enter your street address, your postcode, or use the locate me button on the home page. DryTime will give you a forecast for the area where your washing line actually is.
We would rather be accurate for you than vague for all of London. Sorry not sorry.
Last updated: April 2026 by the DryTime family in Somerset, UK.