Mystery dust cloud over Southport

Yesterday we washed the cars. However, this morning we were surprised to see them covered with a strange greyish dust that seems to have settled in the night.

We went into town later at lunchtime and noticed that others cars in the Morrisons superstore car park had the same deposit on. A lady who lives in Banks (a village about 15 miles away for us in Ainsdale) also told us she had the same thing on her car too.

Was this dust picked up by high winds from some distant desert or something like lime from local farmlands?

How far did this dust invasion spread?

Severe flooding is also occurring as I write (28 June 2012), which may be related to the freak dust advance.