Weather

How does hoar frost form?

Under clear, cold nights in winter, a hoar frost can form.

A hoar frost forms in a similar process to that of dew; the difference being that ice crystals are deposited, as opposed to water, because the temperature of the surface is below freezing.

Hoar frosts most commonly attach themselves to the branches of trees, leaves and grasses, but can also be seen on objects such as gates and flowerpots. Sometimes the deposits can be so thick that it may even look like a dusting of snow has fallen, creating a typical winter wonderland day.  

Dreaming of a white Christmas

Now it’s December, one of the questions we are often asked as meteorologists is “Will it be a white Christmas?” The first thing to clarify, is what exactly is being asked – do you want to know if anywhere in the UK will see a single snow flake or are you envisaging streets and roofs with a dusting of the white stuff when you wake up on 25 December. 

Hot weather on the way

Temperatures are expected to climb into the mid-30°C's next week and while this is very hot weather for the UK, it's not technically a heatwave as theWeather Club explains.

Here in the UK, there is no official definition of a 'heatwave'. Instead, the definition comes from the World Meteorological Organisation who define a heatwave as "when the daily maximum temperature exceeds the average by 5°C for more than five consecutive days."

Weather for athletes: How the weather affects the lives of our athletes

As a sport that predominantly takes place outdoors, the link between athletics and weather is closer than most. Unlike in cricket or tennis rain very rarely stops play, in fact very little actually does. The conditions in which athletes can perform is shown by Colin Jackson's stories elsewhere on this website of chipping the ice from a single lane on a Welsh track in order to train on the frozen ground. Of course athletics is a summer sport, and this is unlikely to be seen at an event, but it illustrates the kind of conditions athletes can go about their business in.