http://www.glidinghotspots.eu/

Glidinghotspots.eu is a platform for exchanging information on thermal
quality of flatland areas. All data is included in one map, which can be
downloaded here. There are already a few older thermal maps from other sources
available, but every of them has one or more disadvantages.
http://Glidinghotspots.eu
tries to combine all advantages and provides thermal information in the open
airspace format, which can be used easily by everyone.