@elilla Yep, that's all good advice. I'd add: make tactical use of windows. We keep the upstairs windows open a crack all the time and the downstairs windows open only in the morning, when it's cooler outside than in.

Keep South-facing curtains closed.

If you can, sleep downstairs.

I'll also be setting up a computer today to enable me to work downstairs next week. The temperature upstairs is going to be completely intolerable.