[zhà nuǎn huán hán]   

乍    暖    还    寒    形容冬末春初气侯忽冷忽热，冷热不定。

乍暖还寒（zhà nuǎn huán hán），形容冬末春初气侯忽冷忽热，冷热不定。

After suddenly getting warmer, the weather has turned cold again

乍暖还寒    乍毛变色    乍寒乍热