I'll be doing some short evening session when I can, since the summer is my best opportunity to fish - I'm on call all through winter, so not as much chance, and I don't like sitting in the cold anyway.
I think the fish will warm themselves then go to a comfortable depth, so still feed and be about, but more likely over drop offs etc.
The key for me is safety, both fish, and fisherman. Make sure you're protected - hat, sun cream etc. Avoid the heat of high noon. Use a bit of common sense. Fish safety - obviously minimise time on the bank. Make sure nets and mats are well wetted with fresh, cool lake water. Take pictures, weigh and return as quickly as possible. I get everything prepped while the fish is in the landing net, then it's a matter of minutes at most to weigh, picture and return.
All that said, it is hot, but let's try and enjoy it as much as we can. We'll all be moaning it's too cold when there's inches of snow around!