Grassfire in New Orleans East

The New Orleans Fire Department battles a 2-alarm grass fire along Terminal Rd. in eastern New Orleans, La., Friday, Aug. 18, 2023. Smoke, high temperatures, and other pollutants are creating ozone in New Orleans and Baton Rouge, prompting health warnings on Friday and Saturday. (Photo by Sophia Germer, , The Times-Picayune)

 STAFF PHOTO BY SOPHIA GERMER

What do you get when you combine , wildfire smoke and sunlight? Ground-level ozone in amounts high enough to cause health problems in both Baton Rouge and New Orleans on Friday and Saturday, according to the federal/state .

The declared action days for both cities on Friday and Saturday for ozone levels that are high enough to be unhealthy for sensitive groups. 

High ozone reading

Air Quality Index reading of 147 for ozone in Baton Rouge at 5 p.m. Friday. At 4 p.m., the index measured 154, high enough to turn the gauge red and prompt a warning of sensitive for all groups. (EPA, h Department of Environmental Quality) 

But at 4 p.m. Friday, the index level actually hit 154 in Baton Rouge, high enough to be considered unhealthy for all. The index level was 108 in New Orleans at 4 p.m., still in the unhealthy for sensitive groups range. 

Those with respiratory problems are advised to avoid being outdoors for long periods of time. The agency also recommended waiting until night to fuel vehicles or operate lawn equipment. 

Ozone warning

Air Quality Index reading of 105 in New Orleans at 5 p.m. Friday. (EPA, h Department of Environmental Quality) 

The forecast for Saturday is for the index to hit 108 in Baton Rouge and 105 in New Orleans, likely during afternoon hours, which is unhealthy for sensitive individuals. 

The air quality forecast messages blame a combination of issues:

  • A strengthening upper level ridge of high pressure moving over the state that will reduce atmospheric mixing and guarantee sunny and hot conditions that promote ozone formation.
  • Calm to light winds most of the day will limit dispersion of pollution from motor vehicles and industry, and the smoke from numerous wildfires that have been burning throughout the state, also enhancing ozone formation. 

While light westerly to southwesterly winds will accompany a weak frontal system that's expected to stall over central h on Saturday, continued sunny and hot conditions -- and that lingering smoke -- will again enhance ozone production by the afternoon hours. 

Active children and adults, the elderly and individuals with respiratory diseases, including asthma, should avoid prolonged outdoor activities and exertion in both cities on Saturday.

High temperature records were broken again on Friday in Baton Rouge, where 102 beat the previous record of 101 set in 2011, and at New Orleans Louis Armstrong International Airport, where 99 broke the previous record of 98, also set in 2011. Slidell also saw a record 101, breaking a previous record of 98 set in 2000. 

"This is just setting the stage for tomorrow (Saturday), which could be the hottest day of the year so far ... because there is a chance mid/late next week could be even hotter," said a 4 p.m. forecast discussion message from the Slidell office of the National Weather Service. 

Excessive heat warning

(National Weather Service)

An excessive heat warning for dangerously hot conditions is in effect on Saturday for the Interstate 10-12 corridor in the Baton Rouge and New Orleans areas, as well as for much of the remainder of the state, which is not unexpected considering Shreveport registered a high of 109 on Friday. 

With moisture also building back into the area, feels-like heat index readings will be between 110 and 115 thrughout the area between 11 a.m. and 7 p.m. on Saturday. 

Heat week

More hot weather ahead, National Weather Service warns. (National Weather Service)

his work is supported with a grant funded by the  and administered by the .

Email Mark Schleifstein at mschleifstein@theadvocate.com or follow him on Twitter, @MSchleifstein.

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