dont worry autumn/winter is not far off and then you ll be moaning your hands are cold!
we dont get many hot working days in this country! just wear your normal polo shirts and shorts,plenty of factor 30 suncream and drink plenty of water and snack on fruit.
if its really hot,take a 5 min break here and there in the shade.
i have white polo shirts for really warm sunny days which keep me cooler than my normal black ones.
i dont seem to sweat that much when working as its easy with xtreme poles and (normally) working a 6 to 7 hour day.