minimum temperature; lowest temperature; (today's) low
最低気温が氷点下になる。
The minimum temperature will drop below freezing.
今夜の最低気温はマイナス3度予報だ。
Tonight's minimum temperature is forecast to be minus 3 degrees.
昨日はこの町で観測史上最低気温を記録しました。
Yesterday, the lowest temperature on record was observed in this town.