The phrase "impromptu evening" is correct and can be used in written English.
It refers to a spontaneous or unplanned event or gathering that takes place in the evening. Example: We had no plans for the evening, but my friends and I ended up having an impromptu evening at the park, watching the sunset and having a picnic.
Frede planned for his patrons what appeared to be an impromptu evening, and volunteers would recite and sing.
If anyone in Las Vegas wants to meet up with the CG crew for wings, beer, and shop talk, drop us a line at tips @ crunchgear.com and we'll try to plan an impromptu evening meet-up on Tuesday night.
Summers are filled with impromptu evening strolls and organized beach parties.
The Journal Constitution reported that soon after, mounted police had halted the impromptu midnight march and 20 people had been arrested.
In his teens, Mr. Hall traded classes at George W. Windgate High School in Crown Heights for impromptu afternoon games of handball.
In an impromptu midnight press conference, surrounded by armed guards, he praised the brigade, and demanded that the Americans cede the job of security.
Bruce Springsteen, who lives in nearby Rumson, thinks nothing of making an impromptu midnight visit to Jack's Music Store to see how his new CD is selling.
The impromptu midnight renaming ceremony means the stadium will revert to being known simply as Stadion Graz-Liebenau, after the district of the city where it is located.
Dear New Kindergarten Mom, This morning, I bundled my boys into the stroller and went out for one last impromptu morning walk.
Fighting for basic democratic freedoms in a repressive Russia, Pussy Riot came to the world's attention with an impromptu midnight concert in Moscow's largest cathedral.
You cannot tell a book by its proverbial cover -- nor should you -- whether you're attending an impromptu midnight drum circle or standing in the queue at the local DMV.
