This morning, I stepped out into a dense mist and it was a glorious omen; I paused to check my pack for sun cream before walking any further. The summer morning mist is a happy one and worth knowing because it offers a positive but counterintuitive sign.
Clouds shield us from the sun’s warmth by day, but act as a blanket and seal in the warmth of the land overnight. After a day of clear blue skies, we experience surprisingly cool nights as the heat radiates unimpeded out of the land, through the atmosphere and into space. The lowest layer of air is touching this cool land and it too cools and then the water vapour in the air condenses to form a mist. This is very common on late summer mornings during sunny spells and many people walk out into a morning of damp air and a veil of poor visibility and assume that bad weather has replaced good. However, the summer morning mist is actually a fair weather sign – it is a reflection of clear skies overnight and although that doesn’t guarantee good weather ahead, it is more likely than not.
If you do wake to a still air misty morning, raise your eyes and look vertically above your head. If you see blue sky there, then you are standing in a thin layer of this cool radiation mist and very shortly the sun will warm the land and the mist will lift and vanish. If it is still white above your head, the sunshine is still a couple of hours off, but keep checking every half an hour and you’ll probably see white turn to light blue and then blue.
You might also enjoy:
Why Is Visibility So Good in the Mountains
The Secret World of Weather – The Book
