I tried climbing (bouldering) for the first time a few weeks ago! Of course, that was the hottest week we've had so far this year and I knew the climbing place was going to be warm. So, I ran up a pair of trousers and altered a top I got in the Next Sale for a super lightweight climbing outfit.
The trousers are the same as my 'lounging trousers' and are made out of t-shirting, to be as light as I could make them.
The top was originally a t-shirt from Next, which I picked up in the sale for £6. I used a tutorial I found on Pinterest to edit it and I'm quite pleased with the end results. Now I have a nice cool work out outfit which I can also use in the gym and for HEMA when it's too hot.
As for climbing - I went up walls with varying degrees of success.