The old Texas weather saying (dating from at least the early 1900s) is: “Only newcomers and fools predict the weather in Texas.”
 
It’s alleged that a newcomer once responded that that’s because there are only two kinds of people in Texas.
 
 
Google Books
I Give You Texas: 500 Jokes of the Lone Star State
by Boyce House
San Antonio, TX: The Naylor Co.
1943
Kessinger Publishing
2004 (reprint)
Pg. 6:
“Nobody but fools and newcomers predict the weather in Texas.”
...
Someone—having rashly prophesied the weather—was reminded of the fools’-and-newcomers’ saying. Replied he:
 
“Come to think of it, they’re the only two classes of people I’ve seen in the State.”
 
Google Books
The American People: Stories, Legends, Tales, Traditions and Songs
by Benjamin Albert Botkin
New York Historical Association
1946
New Brunswick, NJ: Transaction Publishers
1998 (reprint)
Pg. 184:
It has been said that George B. Erath, the famous German pioneer and Indian fighter, was the author of the expression: “Nobody prophesies about Texas weather except newcomers and damn fools.”
 
For many years this has been a favourite gag in Texas social life. It was one of the sells in the old saloon days, and the unfortunate tenderfoot who fell for it always had to set up the drinks to the crowd.
 
One dull, slow evening when things were at an absolute standstill in the saloon, a fresh young guy with a derby hat and store-bought clothes breezed into the place, walked up to the bar ,and ordered a drink. The usual crowd of loafers looked on disapprovingly but said nothing. Leisurely finishing his drink and wiping his mouth with a bright silk handerkerchief, the newcomer said, “Well, I believe it’s going to rain.”
 
The golden opportunity had arrived; the whole crowd was alert and watchful. Then the old nester, the leader in all the local wars of wits, said very fatherly, “My friend, did you know that there were only two kinds of people who prophesy about Texas weather?”
 
“Two kinds of people who prophesy on Texas weather?” mused the stranger. “That’s very queer. Who are they?”
 
Then the old nester, with all the contempt and sarcasm in his power, sneered, “Newcomers and damn fools.”
 
The crowd rose with a mighty shout and gathered around the newcomer shouting, “Haw, haw, haw.” “He got you that time.” “You are it.” “He got you good.” “Set um up. Set um up.” “You owe drinks to the house.” “Come on, set em up.”
 
The young fellow stood smiling at all their hurrah. He was not the least troubled about their demands for the drinks. When the hubbub had died down and they were all properly up against the bar, he said very calmly and slowly, ““You say there are only two kinds of people who prophesy about Texas weather—newcomers and damn fools. You are right. Those ar the only two kinds in Texas.”
   
20 August 1910, Galveston (TX) Daily News, pg. 6, col. 3:
While we do not mean to offend either the fools or the newcomers, we venture to suggest that those who thought Governor Campbell wouldn’t call another session of the legislature are kin to the kinds of people who predict the weather in Texas.
 
29 April 1932, Florence (SC) Morning News, “Texas Hen Turns Weather Forecaster,” pg. 5, col. 5:
CUERO, Tex., April 28 (UP)—A hardworking hen in the barnyard family of Sid Smith, farmer near here, laid an egg bearing the words, “No rain.” Raised surfaces on the perfectly formed egg made the words easily discernible, according to witnesses.
 
The axiom that weather prophets in Texas are either fools or newcomers, has become a tradition. But no rain had fallen in the vicinity of Cuero 22 days after the egg was found.