Here's why:
* The vowel sound in "climate" is short: It sounds like the "i" in "hit" or "sit."
* Long vowel sounds are typically associated with vowels that are spelled with a single vowel letter followed by a silent "e" at the end of the word (like "mate" or "hope"), or with a vowel followed by a consonant and another vowel (like "coat" or "fail").
So, the vowel sound in "climate" is a short "i" sound, not a long vowel sound.