acalenturarse

A regional, mostly rural/colloquial reflexive verb meaning to develop a fever or become feverish — a folk synonym of tener fiebre. Heard in parts of Latin America more than in standard written Spanish.

• El niño se acalenturó durante la noche. — The boy developed a fever during the night.
• Si sigue lloviendo así, te vas a acalenturar. — If it keeps raining like this, you'll come down with a fever.
• La abuela decía que el sereno de la noche te acalentura. — Grandma used to say the night air would give you a fever.

This is folk/regional vocabulary — 'tener fiebre' is what you'd use in standard or medical Spanish, and acalenturarse may not be understood everywhere in the Spanish-speaking world.