@Lockheart It's for 2 days. The heatstroke you mention will affect anyone silly enough to go out and sit in the sun, or not drink enough fluids, or not take any of the measures that are sensible.
The issue that warnings are given is because there are some of the population who are pretty dim and don't take sensible precautions.
(This week I saw an elderly, disabled woman (80s) in her motorised buggy , with what looked like her daughter walking alongside her, and she wasn't even wearing a sunhat and it was over 30C in the park.)
Many people will work from home as they are already. I expect many companies will make allowances if staff can't get to work safely, and they may also have invested in aircon.
I despair at how worked up people (usually younger who weren't around in the 10 week heat wave of 1976) get over 2 days of hot weather.
In 1976, water was rationed and people used standpipes. No one made a fuss. It went on for weeks and weeks. Former colleagues of mine were teaching in classrooms then.