noun
laundry index
A numerical indicator used in weather forecasts to show how suitable the weather is for drying laundry outdoors. Higher values mean better drying conditions.
明日の洗濯指数は80%で、よく乾きそうです。
Tomorrow's laundry index is 80%, so clothes should dry well.
洗濯指数が低い日は部屋干しにしています。
On days when the laundry index is low, I dry my laundry indoors.
Compound of 洗濯 (せんたく, 'laundry') and 指数 (しすう, 'index'). A modern term used in weather forecasting.