harbinger

Dictionary result for harbinger
/ˈhɑːbɪn(d)ʒə/
noun
a person or thing that announces or signals the approach of another.
"witch hazels are the harbingers of spring"
synonyms: herald, sign, indicator, indication, signal, prelude, portent, omen, augury, forewarning, presage, announcer; forerunner, precursor, messenger, usher; avant-courier; literaryforetoken