You can say “si-kah-da” or “si-kay-da”. Either pronunciation is correct. The pronunciation changes depending on your regional accent.
Around New York and New Jersey folks pronounce it “si-kah-da”. William T. Davis pronounced it “si-kah-da”. Davis was a naturalist and entomologist located in Staten Island, NY, active in the late 1800â€²s and early 1900â€²s. Davis collected the largest collection of cicadas in the United States. The collection is currently housed at the Staten Island Museum. Davis described over 100 cicadas in his career — he should know what he’s saying. :)