Weather in Letchworth Garden City now
How unusual are the current readings?
Forecast · next 12 hours ?
The Zambretti forecaster, a pocket dial sold by the instrument makers Negretti & Zambra from 1915: set to the pressure, which way it’s going, the wind and the season, it gives one of 26 forecasts. How good is it?
How it’s done:
The Zambretti forecaster at 9 am and 9 pm each day, from the barometer as it was then: did 0.2 mm or more of rain fall in the 12 hours after? A mark below shows each it got wrong.
Last 24 hours
What's a front?
A front is the boundary between two air masses. As a cold front passes, colder, drier air arrives: pressure that has been falling turns to rise, and the temperature and dew point drop, often with a gust and a burst of rain. A warm front brings milder, moister air, usually after hours of falling pressure and rain. An occluded front, where a cold front has caught up with a warm one, brings a spell of rain with little change in the air: the station sees only a deep dip and rise in pressure, with rain at the bottom of it.
These are found automatically from this station's readings alone, by looking for those changes beyond what's usual for the time of day and year. So they're "likely": some fronts will be missed, and now and then a heavy shower may look like one.