New York City-born comedian George Carlin (1937-2008) performed the bit “Al Sleet, the hippy-dippy weatherman,” containing the memorable joke:
 
“Tonight’s forecast: dark. Continued dark tonight, turning to partly light in the morning.”
 
Carlin’s joke dates to at least 1972, when it was included in the audiobook FM & AM, and to 1978, when he told it in a filmed performance.
 
   
Wikipedia: George Carlin
George Denis Patrick Carlin (May 12, 1937 – June 22, 2008) was an American comedian, writer, social critic, and actor who won five Grammy Awards for his comedy albums. Carlin was noted for his black comedy as well as his thoughts on politics, the English language, psychology, religion, and various taboo subjects. Carlin and his “Seven dirty words” comedy routine were central to the 1978 U.S. Supreme Court case F.C.C. v. Pacifica Foundation, in which a 5–4 decision by the justices affirmed the government’s power to regulate indecent material on the public airwaves.
 
He is widely regarded as one of the most important and influential stand-up comedians of all time: one newspaper called Carlin “the dean of counterculture comedians.”
 
OCLC WorldCat record
FM & AM
Author: George Carlin
Publisher: N.Y., N.Y. : Little David, 1972.
Edition/Format:   Audiobook on LP : LP recording : English
(The joke is at 5:45 on Side 2 Track 5 “The 11 O’Clock News.”—ed.)
     
Google Books
1,911 Best Things Anybody Ever Said
By Robert Byrne
New York, NY: Fawcett, Columbine
1988
Pg. ?:
518
Weather forecast for tonight: dark.
George Carlin
   
OCLC WorldCat record
George Carlin again!
Author: George Carlin; MPI Home Video (Firm); Home Box Office (Firm)
Publisher: [S.l.] : MPI Home Video, [©2001]
Event notes: Performance in the round at the Celebrity Star Theater in Phoenix, July 23, 1978.
Contents: Al Sleet, the hippy-dippy weatherman.
 
YouTube
George Carlin ‘The Hippy Dippy Weatherman’
CappyNJ’s channel
Uploaded on Oct 12, 2007
George Carlin revisits Al Sleet, the Hippy Dippy Weatherman from 1978’s ‘George Carlin Again’.
1:40
“Tonight’s forecast: dark. Continued dark tonight, turning to partly light in the morning.”
   
Google Books
Dictionary of Quotations
By M..Kumar
New Delhi: S. B. Nangia
2008
Pg. 251:
Weather forecast for tonight: dark. Continued dark overnight, with widely scattered light by morning.
George Carlin
 
Google Books
Tweet This Book:
The 1,400 Greatest Quotes of All Time in 140 Characters Or Less
Edited by Sayre Van Young and Marin Van Young
Berkeley, CA: Ulysses Press
2011
Pg. 162:
Weather forecast for tonight: dark.
George Carlin
 
YouTube
George Carlin: FM & AM - The 11 O’Clock News
GeorgeCarlinCentral
Uploaded on Jul 3, 2011
FM & AM is an album by American comedian George Carlin. This album was originally released in 1972 on the Atlantic Records subsidiary label Little David Records, later reissued on Carlin’s Eardrum Records label. It was also included as part of the 1992 Classic Gold collection, and The Little David Years (1971-1977) box set.
 
FM & AM won the 1972 Grammy Award for Best Comedy Album.
5:43
“Tonight’s forecast: dark. Continued mostly dark tonight, turning to widely scattered light in the morning.”