Feeling under the weather (or simply under the weather) is an idiomatic expression, meaning a person is feeling sick, unwell, demotivated or sad.
The expression can be used in the most simple, everyday situations, like when you catch the flu, as well as in more drastic situations when somebody feels lethargic or is not in a stable state of mind.
The idiom is well-recognized and it is accepted to use it both in formal and informal situations.
The expression originates from the old times, when traveling and transportation primarily happened with sailing boats and ships.
Sailors came up with the original expression,“feeling under the weather-bow”, which they used when they felt hungover or seasick and sought shelter under the deck of the ship from the elements. The weather-bow is The bow of a ship that is turned towards the wind.
Today, feeling under the weather is primarily used in sickness-related situations. There are many postcards, motivational posters and other graphic design content online that utilize the idiom as a template.
The expression is also featured and explained on various YouTube channels that teach English phrases to foreign speakers.