4 sentences

1. 入冬以来，气温直线下降。

   rù​dōng yǐ​lái, qì​wēn zhí​xiàn xià​jiàng.

   Temperatures have plummeted since the beginning of winter.

   Source: Dong Chinese Dictionary

2. 快要入冬了。

   kuài yào rù​dōng le.

   It'll be winter soon.

   Source: OpenSubtitles

3. 入冬以后，院子里的花木逐渐憔悴了。

   rù​dōng yǐ​hòu, yuàn​zi lǐ de huā​mù zhú​jiàn qiáo​cuì le.

   After winter set in, the flowers and trees in the yard gradually withered.

   Source: Dong Chinese Dictionary

4. 受冷空气影响，今天的气温创下了入冬以来的新高。

   shòu lěng kōng​qì yǐng​xiǎng, jīn​tiān de qì​wēn chuàng​xià le rù​dōng yǐ​lái de xīn​gāo.

   Affected by cold air, today's temperature hit a new high for this winter.

   Source: Dong Chinese Dictionary