https://freesound.org
https://sound-effects.bbcrewind.co.uk/search
https://www.nps.gov/yell/learn/photosmultimedia/soundlibrary.htm
https://soundbible.com/
https://www.partnersinrhyme.com/pir/PIRsfx.shtml
https://www.soundgator.com/
Let me know if you find any other good sources.
https://ytmp3.cc
https://www.y2mate.com
https://www.flvto.biz
https://x2download.com
https://320ytmp3.com
This Wind pack looks promising: Wind pack
thunder sheets done https://www.youtube.com/watch?v=rG3YRGwNvy4 (needs editing) done https://www.youtube.com/watch?v=NNUMqm_OTfQ (needs editing)
thunder rolling done https://www.youtube.com/watch?v=AuNnG2J8LMc
a little (gentle) thunder (v1,v2,v3)
lots of thunder
distant thunder done https://www.youtube.com/watch?v=bvjUJg1rzEA
thunder (v1, v2, v3) done https://www.youtube.com/watch?v=T-BOPr7NXME done https://www.youtube.com/watch?v=qOHuT5njtRA (need editing) https://www.youtube.com/watch?v=gTOgniemAC4
https://sounds.aptwordmedia.com/app.zip