Mexicali surpassed Monday the 200 point threshold according to reports of the Imperial County monitoring network.
The station located in Colegio de Bachilleres read 202 points at 10 p.m. Sunday.
Such level is considered as very unhealthy.
The authorities had classified such level as especially dangerous for minors, elderly and residents with respiratory and heart issues.
The authorities also recommend avoiding holding outside activities for over three hours.
At the same time the station located in the Autonomous University of Baja California read an unhealthy level, while the one in Calexico read a moderate level. Mexicali has reported bad air quality conditions since Friday evening.