Yeah summertime ground water temps are a freaking challenge. What I do is to put a sanitized frozen water bottle (or 2)in the kettle once the cooling levels off, to get the extra few degrees of cooling I need. I stir thoroughly to shorten cooling times anyway, but it's extra important here, to avoid temp stratification. I cool 2 or 3 degrees below my target fermentation temp, to account for the temp spike around high krausen.