Everything you need to know about freezing rain
Supercooled droplets freeze immediately when they hit surfaces close to or below freezing.
Freezing rain has struck Great Britain as the country continues to struggle through the prolonged cold snap.
Here is an explainer on the rare weather phenomenon currently trending on Twitter.
– What is freezing rain?
Freezing rain is formed from “supercooled” droplets that hit the ground in liquid form. When the droplets hit surfaces that are close to or below freezing, they freeze on impact.
– How is it caused?
Snow, ice, sleet or hail passes through a layer of air that is warmer than 0C and turns into liquid droplets. These droplets become supercooled when they then fall through a layer that is below freezing closer to the ground, but remain in liquid form. When they hit a surface that is close to or below zero, they freeze immediately.
– Where has it been seen?
It was spotted in the South West overnight and Friday morning. Forecasters predict it will be working its way further north over the weekend as warm air spreads up from the South.
– How is it different from snow?
Snow forms when tiny ice crystals in clouds stick to each other and form flakes, which then fall to the ground when heavy enough. Freezing rain may start off as snow but at some point it passes through different temperatures to become a supercooled liquid.
– What does it look like?
Photos shared on Twitter show frozen water droplets hanging off branches and flower petals – seemingly in suspended animation. On flat surfaces, the droplets can form a sheet of ice.
One badly affected area is southwest England. After #snow and #freezingrain last night, black #ice will make it treacherous through the next 12 hours, only gradually melting during Saturday. Take care and stay #weatheraware pic.twitter.com/Te4tfFToPJ— Met Office (@metoffice) March 2, 2018
– Why can it be dangerous?
The ice is clear and can be slippery and hard to see. It has been described as “one of the greatest challenges any driver could face” by RAC traffic spokesman Rod Dennis. Motorists should slow down gently, use lower revs by getting into a higher gear and avoid braking on bends.
– How common is it in the UK?
Not very. Here we are more likely to see rain falling on surfaces that have already frozen, or rain falling on ground which then freezes as the temperature drops overnight.