Other forms: rainier, rainiest
Rainy means with lots of water falling from the sky. A rainy day, rainy season, rainy weather.
Save it for a rainy day means keep it for hard times, which is one of the oldest money proverbs in English. The rainy season in the tropics is a matter of months rather than days. Note the y ending, which turns a noun into an adjective — rain and rainy, wind and windy.
1adjectiverainyWith a lot of rain falling.
“On rainy days, the children play board games indoors.”
rainy is a quality of weather.
Old English regnig is rain plus the -ig ending that makes adjectives, the modern -y.
Proto-Germanic
*regnagaz — rainy
Proto-West Germanic
*regnag
Old English
reġniġ
Middle English
reyny
English, today
rainy
From Middle English reyny, from Old English reġniġ, from Proto-West Germanic regnag, from Proto-Germanic regnagaz (“rainy”), equivalent to rain + y. Cognate with stq rienig (“rainy”), West Frisian reinich (“rainy”), Dutch regenig (“rainy”), German regnig (“rainy”), Swedish regnig (“rainy”).
Etymology from Wiktionary, CC BY-SA