The smoke from hundreds of agricultural burns in Mexico has been making its way to the Rio Grande Valley causing hazy conditions.

The smoke is also causing moderate to unhealthy air quality conditions for sensitive groups, the National Weather Service Office in Brownsville reports.

“At this time of the year, and continuing through around or just after Memorial Day, periods of hazy or ‘milky’ skies are expected, and air quality will often be in the ‘moderate’ range with a few days in the ‘Unhealthy for Sensitive Groups’ range,” writes Barry Goldsmith, warning coordination meteorologist for the NWS.

“The large number of fires along the crescent of eastern Mexico through the Yucatan will continue to produce smoke/soot that will frequently be trapped under the inversion, which will continue to be an issue through next week,” writes Goldsmith.

He added that although there may be breaks when low level winds switch northeast/north, the return of southerly flow and unseasonable heat and humidity will keep the threat of USG (Unhealthy for Sensitive Groups) or AQI (Air Quality Index) going on for awhile.

People with lung or heart disease, older adults, teens and children should avoid strenuous outdoor activity, keep outdoor activities short, consider moving physical activities indoor or rescheduling them. Everyone should choose less strenuous activities such as walking instead of running, shorten the time of your outdoor activities and be active outdoors when the air quality is better

Goldsmith said the worst affected locations will be along US/77 where drier air and prolonged north/northwest winds will not penetrate. This includes Cameron and Willacy counties. Hidalgo and Starr counties will see less frequent USG periods.

Air Quality Index is divided into six categories. Each category has a specific color:

>>Green — Good — 0 to 50 — Air quality is satisfactory, and air pollution pose little or not risk

>>Yellow — Moderate — 51 to 100 — Air quality is acceptable. However, there may be a risk for some people, particularly those who are unusually sensitive to air pollution

>>Orange — Unhealthy for sensitive groups — 101 to 150 — Members of sensitive groups may experience health effects. The general public is less likely to be affected

>>Red — Unhealthy — 151 to 200 — Some members of the general public may experience health effects; members of sensitive groups may experience more serious health effects

>>Purple — Very unhealthy — 201 to 300-Health alert: The risk of health effects is increased for everyone.

>>Maroon — Hazardous 301 and higher — Health warning of emergency conditions: everyone is more likely to be affected.

Goldsmith states an AQI above 200 affects everyone and may require alerts.

To find out what the air quality is where you live, visit https://airnow.gov