Europe is apparently undergoing a storm of Noctilucent Clouds (NLC's). They are also now being reported in parts of the US!!
I have attached two pictures from
www.spaceweather.com where you can find more pics and info on how to look for NLC's.
Picture 1 from Piotr Majewski and taken in Torum, Poland
Picture 2 is from Dan Earl and taken in Grass Valley, Oregon
Mark