Sprummer (spring + summer)

“Sprummer” (spring + summer) is a portmanteau word that has been printed on many images.
   
“Sprinter” (spring + winter) is a related term.
 
         
Wiktionary: sprummer 
Etymology
Blend of spring +‎ summer
Noun
sprummer (uncountable)
1. Transition period between spring and summer: late spring.
   
Newspapers.com
14 April 1936, Chicago (IL) Daily Tribune, pg. 14, col. 1:
OUR GENTLE SPR-INTER.
Whether it’s spring because it’s baseball or baseball because it’s spring, it’s now both, or may be if publication of the statement follows quickly enough upon the making of it. We’ve often known it to be spr-inter. The change occurred right in the uttered word. The wind shifted. Sometimes it’s only spr-all and again it may be spr-ummer. it seldom remains spring, but whether one thing or another it’s a season of interesting variety.
 
Google Groups: alt.religion.wicca.moderated
HOW Many Seasons?!
Baird Stafford
Aug 23, 2009, 4:12:07 AM
Somebody named Tim Entwisle of Sydney’s Royal Botanic Gardens says that a mere four seasons isn’t nearly enough for Oz. He wants “Sprummer” and “Sprinter” as well, and thinks that each district of the continent ought to have as many seasons as it needs - up to eight, at least.