El calor aprieta.

This isn’t the right word for being turned “on.”

English Translation

The heat is on.

I think it refers to the current weather, a heatwave.

There is an English expression/idiom “The heat is on” which means the pressure to perform is becoming greater and greater. Since apretar is to apply pressure, this might be a translation of that expression/idiom, but I don’t know for sure.

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