Anyone suffer in the heat?

Went out for a half century today and my times were garbage. Been riding pretty well recently and thought I’d do ok today but I was knackered about a third of way in. Big mistake was probably only taking one bottle and setting out about 10. Just kind of grinded out the rest of the trip once the big hills were out of the way and found myself dropping into gears I don’t normally use, legs just weren’t having it. 

Putting it down to the heat, as I’m not a great fan of hot weather.