English: Rimed post near Cairn Gorm summit. Rime builds up in clouds when supercooled droplets (liquid water below freezing) carried by the wind impact on any obstacle and immediately freeze. The ice therefore builds out towards the wind, like a flag in reverse, so here the wind has been from the right.

From the length of the ski stick (just over 1 metre), I estimate about 45 cm of rime at the top of the post. There is usually more rime higher above ground level since the wind is stronger away from the surface.

This shows why cairns and posts cannot be relied on as waymarkers in winter - in a whiteout this would be invisible!