From 19-21 February 2013, noctilucent clouds were observed in the UK, Denmark, Norway and the Netherlands. Since these clouds are usually only seen in summer, it is suspected that they may be the result of comet dust deposited in the upper atmosphere by the Chelyabinsk/Chebarkul meteor or comet fragment explosion over Southern Russia on 15 February.

The following images were submitted to spaceweather.com
Image
© Terry Parker
Image taken by Terry Parker on Feb. 20, 2013 from above Birmingham, UK. 'I am an airline pilot in the UK and I occasionally see noctilucent clouds. Usually during the summer at about midnight looking North. But yesterday (20 Feb 13) I was very surprised to see them looking south towards France and so close to sunrise.'

Image
© Tom Axelsen
Photo by Tom Axelsen, Copenhagen area, Denmark

Image
© Henrik Bondo
Photo by Henrik Bondo, Denmark

Image
© Jan Tromp
Taken by Jan Tromp on February 21, 2013 @ Beverwijk, Netherlands

Image
© Margaret Hughes
Taken by Margaret Hughes on February 19, 2013 @ Askam-in-Furness, Cumbria, England.