The past few days have been warm then cold again — easy to catch a cold.
Tips
history
From Li Qingzhao's 《声声慢》 (Song dynasty): "乍暖还寒时候,最难将息" — "at that warm-then-cold time, it's hardest to recover." One of the most quoted lines in classical ci poetry.
mistakes
还 here is read huán (4th tone, "return; again"), NOT hái ("still"). The phrase means "just warm, then cold returns."