This is an irregular verb. It follows the conjugation pattern of the verb sentir.
Stem Change: e ie (advierto) - e i (advirtió)
Gerund: advirtiendo
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.