The Voice of Spalding and South Holland
A rare form of cloud that shimmers with rainbow colours was spotted over the district this evening (Thursday December 12).
Nacreous clouds, ‘mother of pearl’ or Polar Stratospheric clouds need special cold conditions to form, usually those in areas around the poles.
Occasionally, cold polar air which is locked in place by strong winds high up in the atmosphere – called the polar vortex – sinks south to our latitude.
They’re formed by tiny ice crystals around 12 to 19 miles above the earth’s surface where the temperature is -80C (-112F).
