A lot depends on the particulars of the weather, humidity and wind make a big difference, if air movement is low and humidity is high water may not evaporate rapidly enough to provide any cooling.
Wetting your clothing can work well in Arizona where humidity is typically low. Do the same thing in humid Florida and you will likely regret it.

If you don't know which way to go wet a bandana or small cloth and drape it over you. If it is col and stays cool evaporation is working for you. If it clings so you are now both hot and wet it is likely better to save the water for drinking.