A four-character idiom describing a pattern of weather in late winter/early spring where roughly three cold days are followed by four warm days; used to describe seasonal fluctuations.
このところ三寒四温で、朝晩はまだ冷えるが日中は暖かい。
Lately it's been the 'three cold, four warm' pattern; it's still chilly in the mornings and evenings but warm during the day.
三寒四温の時期は体調を崩しやすいので注意が必要だ。
You need to be careful during the three-cold-four-warm period because it's easy to get sick.
天気予報士は三寒四温が続くと春の訪れが近いと説明した。
The weather forecaster explained that if the three-cold-four-warm pattern continues, spring is near.