Tonight temperatures will fall well below freezing (point).

今夜温度将远降至冰点以下。

《牛津词典》

If temperatures overnight are already very close to the freezing point, then this drop of just a few degrees can take the temperature below freezing.

如果夜间的温度已经非常接近冰点，那么仅仅下降几度就可以使温度降到冰点以下。

youdao

It's 15 degrees below freezing.

温度是零下15度。

《柯林斯英汉双解大词典》

Skiles, 49, and also praised first responders who acted quickly to minimize passengers' injuries in below-freezing temperatures.

CNN: Recorders recovered from Hudson in 'excellent' condition

They describe him as highly intoxicated at the time and not wearing a shirt despite below-freezing temperatures.

WSJ: Cops: Witness IDs Giants owner's nephew in assault

Skiles, 49, as well as rescuers, who acted quickly to minimize passengers' injuries in below-freezing temperature and frigid water.

CNN: Investigators find feather, other evidence on downed plane