Humidity has also been on the rise each day, but until today has dropped enough in the afternoons to keep the heat index near or below 100. As the humidity starts to climb though, heat indices will reach 105+ today through the weekend (at least). This has prompted the issuance of a Heat Advisory through 10pm tonight and we will likely see advisories continue through the weekend as high temperatures remain in the upper 90s into next week.
Interestingly, the earliest 100-degree reading ever seen at Memphis International Airport was on June 6 in 1977. Though 100 is not in the forecast, there is a small chance we could touch the century mark this weekend. If we do that, it'll be the earliest 100 degree temperature ever in Memphis.
The hazy part of the 3H formula can be seen in the snapshot from FOX-13's downtown SkyFox cam shown above and is due to increasing levels of ozone and pollution trapped in the lower atmosphere under sinking air created by persistent high pressure overhead. Without much wind, the pollution sits in place rather than being dispersed. Ozone is chemically created from pollutants from cars, factories, and other industry reacting in the presence of sunlight and heat. It then becomes a pollutant (more on ozone basics).
For today, the level of ozone is forecast by the Shelby County Health Department Air Quality Improvement Branch is high enough that a Code Orange Ozone Advisory has been issued. Code Orange means that the air is "Unhealthy for Sensitive Groups," including those with respiratory problems under normal circumstances (asthma, lung disease, etc.) and active adults and children and the elderly. The Health Department urges everyone to reduce time spent outside and limit prolonged exertion, reduce trips and carpool, and schedule outdoor activities in the morning and evening, avoiding the hottest part of the day.
For more information on ozone and air quality, visit the following links:
- MWN's Air Quality Forecast page
- Shelby County Health Department Air Quality Improvement Branch
- AirNow.gov - excellent resource
- EnviroFlash - air quality notifications
- Environmental Protection Agency
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