U.S. stocks hit new all-time highs last week, with four consecutive weeks of gains, but one chief investment strategist warned investors that the recent rally could cool as temperatures do.

"We remember all those romances back at summer camp; they were exciting, they were hot, they were thrilling but when summer camp ended, they ended," Michael Arone, State Street Global Advisors chief investment strategist told CNBC's "Squawk on the Street" Monday. "When summer turns to fall, this particular rally will begin to slow down."