This is an irregular verb. It follows the conjugation pattern of the verb sentir.
PresentPresente
El cartel advierte del peligro en la playa.
The sign warns of danger at the beach.
PreteritePretérito indefinido
Te advertí que iba a llover.
I warned you that it was going to rain.
ImperfectPretérito imperfecto
Mi madre siempre nos advertía del frío.
My mother always warned us about the cold.