Can you tell me which website?

[MaryMotherOfCheeses]

To compare average weather in, say, August, between two locations in the UK

I've googled, honest, and can't find anything easy.

Does such a thing exist?

I've not found something to compare different monthly averages, but this site does historical data for individual days for different locations.

Perfect.

It does compare if you open it in two tabs and look at different places

Thank you.

You are welcome :) glad it Can do the right thing for you.