West Texas Rain (a sandstorm)

A sandstorm (or dust storm) has been called “West Texas rain.” The humorous bit of slang is not based on fact; it rains in West Texas much more often than you’ll see a sandstorm.
 
 
Google Books
I Give You Texas!
500 Jokes of the Lone Star State
by Boyce House
San Antonio: Naylor Company
1943  
Pg. 8:
A West Texas rain: a sandstorm.
       
1 July 1968, Dallas Morning News, section C, pg. 7:
Ted Sheehan, forecaster at the U.S. Weather Bureau at Lubbock Municipal Airport, discovered that dust storms—sometimes called “West Texas rain”—occurred only 2 per cent of the time from 1949 through 1967.
 
Google Books
Paisanos, a Folklore Miscellany
edited by Francis Edward Abernethy
Austin, TX: Encino Press
1978
Pg. 93:
Dust storms have long been called “West Texas Rain.”