Mexico is facing an extremely heavy season of brush and forest fires, with 4,425 blazes recorded so far this year.

The federal Environment Department said Wednesday that 3,800 firefighters are combatting an average of about 100 fires per day in brush, scrub, agricultural and forest land throughout the country. Fire risk is highest in the spring for much of Mexico because the summer rainy season has not yet started.

About 378,000 acres (152,952 hectares) have been affected so far.

The smoke has been so bad it triggered a pollution alert in Mexico City this week.

On Monday, NASA's Discover the Earth Observing System Data and Information System featured images showing the smoke plumes over southern Mexico in its #NASAWorldview Twitter feed.