It’s not often we get cold snaps in the fens. We’ve just had one with temperatures down to -6 C. Along with sub zero temperatures there’s been fog which persisted during the day keeping temperatures well below zero during daylight hours. These types of conditions are ideal for the formation of hoar frost.
Hoar frost on a reed
What is hoar frost?
Hoar frost is a type of feathery frost that forms when water vapour in the air comes into contact with surfaces that are already below freezing. Ice crystals form and the ice continues to grow as more water vapour is frozen. Sub zero temperatures combined with a persistent fog are ideal conditions for hoar frost to form.
Hoar is an old English word that refers to the appearance of old age. Hoar frost looks like white hair or beard hence the word hoar when describing this type of frost.
Hoar frost can be great for photography while it lasts. I visited Woodwalton Fen when there was hoar frost in the trees. With conditions like this it’s like a magical winter wonderland.
A tree covered in hoar frost
Woodwalton Fen looks like a magical winter wonderland
Snow and frost at Woodwalton Fen
After a couple of days the fog lifted and the hoar frost quickly thawed.
The thaw has started at Woodwalton Fen
Even a weak sun is enough to melt the hoar frost.
A weak sun is enough to start the thaw at Woodwalton Fen
Fen Photos. 
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