Juice will be thinner; especially a concern when using carto tanks. Last summer (it hit 100F more than a few times...) I was vaping 80PG in single-hole cartos & didn't frequently have problems... now I am using PGA-based flavorings at high %; my juice was water-thin in the winter, I am hoping summer won't wreck my tanks.
With tanks, I have found they seem to work fine when temps are consistent - it is in transitional seasons, when temps and atmosphere pressures or whatever go all over the place, that my tanks go haywire.