Even though the worst of the heat wave hasn't hit yet, Friday was still sweltering enough to pop up the pavement.
A part of Route 202 near King of Prussia buckled in the heat late Friday afternoon. Two pieces of pavement pushed up at a seam, forming a small but impassable tent.
The cause was extreme heat conditions, according to a PennDOT spokesman.
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The buckle happened on the southbound lanes near Henderson Road. Cars had to creep onto the shoulder to avoid it, and the result was a traffic mess that lasted throughout rush hour.
Crews expected to be on the scene into Friday evening.