The spelling of the word "humidnesses" can be a bit tricky to decipher. In IPA phonetic transcription, it would be spelled /ˈhjuːmɪdnəsɪz/. The double "s" at the end is due to the word being plural, indicating multiple instances of "humidness". The "d" after the "m" is a result of the pronunciation, where the "m" and "n" sounds tend to blend together. Overall, "humidnesses" is not a commonly used word, but it does exist for situations where multiple instances of humidness need to be referred to.
The word "humidnesses" is derived from the root word "humid", which originates from the Latin word "humidus". "Humidus" means "moist" or "damp". The -nesses suffix is added to the base word "humid" to form "humidnesses". The -nesses suffix is a plural form of the noun suffix -ness, which indicates the quality or state of being humid.