Refers to weather conditions, specifically whether it is clear or rainy. Often used in set phrases like 晴雨にかかわらず (regardless of the weather).
Regardless of the weather, tomorrow's event will be held as scheduled.
The weather patterns in this region have been changing in recent years.
barometer
Compound of 晴 (clear weather) and 雨 (rain). The reading せいう is the on'yomi for both characters.