Blue 'noctilucent' clouds are appearing further south than ever seen before, and pollution may be a cause

Cloud watchers have recently been given record-breaking glimpses of the rarest clouds in the skies. Stunning rippled blue clouds have been forming in the highest reaches of the atmosphere over Europe and the U.S.. These clouds are normally only seen around the poles, but this summer is set to be the best observing season in years—they have already been seen at the lowest latitudes ever recorded.

source https://www.lifetechnology.com/blogs/life-technology-news-blog/blue-noctilucent-clouds-are-appearing-further-south-than-ever-seen-before-and-pollution-may-be-a-cause