I was wondering if you had a Rapid-Strike Urshifu in sunny day. Would his surging strikes’ damage be halved because of the sun, or do critical hits ignore that as well? Just wondering.
I believe that a critical hits are not affected by direct stat stage changes, but the critical hit damage would still be affected by the affect of the weather. This is the conclusion I came to after running it through smogon's damage calculator. It returns a 0% damage which I am not sure why that is the case but, it appears that weather affects crit damage whereas direct stat stage increase/decrease will not affect crit damage.
Damage calculator