"temperature plunges" is a perfectly correct and usable phrase in written English.
You could use it when discussing a sudden and dramatic drop in temperature. For example, "As the cold front moved in, the temperature suddenly plunged 10 degrees Celsius."
The less fortunate take shelter in the sewers, where they huddle beside hot-water pipes when the temperature plunges to 40 below.
Russian television crews stand for hours on a muddy patch at the base, or even ankle deep in snow when the temperature plunges below freezing, waiting for the military press service to whisk them into Chechnya by helicopter.
The 170-metre slope is lined with real snow and as I walk through the doors the temperature plunges – I can see my breath puff out in front of me.
Baldly described by Urban Dictionary as "obnoxious partying males," the bros can't wait to get down to their short shorts, though when the temperature plunges after dark they might put on a singlet with an obnoxious slogan on it if pushed.
When the temperature plunged, the self-draining hydrant in the yard froze up.
A "blue northern" front rolled in, sending the temperature plunging and wind gusting.
If the animals had not previously been exposed to PLA2, their temperature plunged, sometimes fatally.
That day the temperature plunged to -26C at Walton-on-Thames, one of the coldest days for generations.
(It was 30 degrees outside when I began the trip, and the temperature plunged that night to 10 degrees).
Thirty-three years later, on Christmas Day 1980, the temperature plunged to 1 below, with winds of up to 40 miles an hour.
On a recent night in Minneapolis, as the temperature plunged toward sixteen below zero, an unlikely midwinter carnival took place in Orchestra Hall.
