A few years ago, they filmed “The Dark Knight” in Chicago. I forget the exact timing, but it was a warm summer month — probably July or August. Fast forward to today, and they’re filming “Transformers 3” here. The temperatures? Consistently around 90 degrees every day, which makes things harder on the actors, extras and crew — not to mention all the pricey equipment they use.

Apparently, producers in LA think that northern cities like Chicago and New York are cold all year round, since they keep scheduling these film shoots during the summer months that locals know can get brutally hot. If the people in charge just looked at the historical averages, they’d see that the spring and fall are a lot milder — and there’s fewer tourists to get in the way of things. Scheduling an elaborate and expensive movie shoot in the summer just doesn’t make sense.

What’s that? You’re stuck with some bizarre contract provisions that require you to film in a big city during the summer? In this unlikely case, try San Francisco. The financial district can pass for Any Big City USA, and the weather rarely seems to get above 70 degrees — even when New York and Chicago are suffering through 90 degree days.