Looks like Sunday could be pretty warm. Above 16 or so degrees your performance will start to suffer. If you become dehydrated then your performance will suffer EVEN more.
I just did a quick FREE online sweat test with Precision Hydration and may well put some of it into action for Sunday. We’ll see.
One interesting aspect of the sweat test is that (it’s free!) it tells you what to do about your likely level of hydration. Of course they also try to sell you stuff but that’s how these things work. I think their additional more personalised service is probably too much to think about before this Sunday. Maybe for your next HM?
Anyway here is my summary from them.