I've always pronounced "theater" with a long a sound, such as in the word "ate." Generally, most people here in San Diego pronounce the "a" as a short I sound, as in "is" and put the stress on the "e." I recently noticed that my grandfather, originally from Kansas, pronounces this word like I do, so I most likely acquired it from him. Is this just a random pronunciation, or is this common in Kansas, or the Midwest?
Welcome, Audra.
Your pronuncation is not random at all. Merriam-Webster lists it as "oftenest in Southern" with the stress either on the first or second syllable. Merriam-Webster: theater
the ·ater :-- noun ˈthÄ“-É™-tÉ™r, ˈthÄ“É™-, oftenest in Southern ˈthÄ“-ËŒÄ- also thÄ“-ˈÄ-
I don't think that I would be out of place to say that unless your speech is Southern, this pronuncation would sound out of place. If I were to hear someone pronounce it with the "long a" -- even my southern friends -- I would consider if they were mocking or adopting a caricaturish accent, such as the Beverly Hillbillies.