On first day of summer, heat wave intensifies and heads for the South
The heat wave that has blanketed a vast swath of the U.S. since early this month is now entering its third week, and it is intensifying in the Midwest before taking aim at the South and Southeast for the rest of the week.
The big picture: Combined with sultry levels of humidity at times, air temperatures in the low triple-digits will bring dangerous heat to cities including Nashville, Tennessee; Atlanta; Birmingham, Alabama; New Orleans; Houston and Dallas. Heat advisories were in effect for 42 million residents on Tuesday afternoon, from Michigan to New Orleans.
- More advisories, along with strongly worded excessive heat warnings, are likely to be issued into Wednesday as the heat builds and slides south.
- Climate change makes extreme heat events more likely to occur and causes such events to be longer in duration and severity as well.
Zoom in: Through June 28, about 62 million Americans are forecast to see air temperatures reach or exceed 100°F, from South Carolina to Oklahoma and Texas.
- During the same time frame, an estimated 232 million people from the Midwest to the Central states as well as the South and Gulf Coast, are forecast to see temperatures exceed 90°F.
- This comes in addition to the tens of millions who have already seen hot temperatures during the past few weeks, from the Southwest to the Plains states and Midwest in particular.
Why it matters: Heat waves can be deadly, with heat illnesses striking the most vulnerable, from the homeless to the elderly, along with poorer residents who cannot afford air conditioning.
What's next: On Wednesday, temperature anomalies of between 10-15°F above average are forecast from the Ohio Valley to the Southeast, with numerous daily records expected to be tied or broken, including in Atlanta.
- Wednesday and Thursday look to be the hottest days in Georgia, South Carolina, Alabama and Mississippi, with high temperatures potentially reaching 105°F and heat indices up to 110 to 115°F. Atlanta could see back-to-back 100-degree days, along with Huntsville and Birmingham, Alabama.
- After Thursday, the high-pressure area, also known as a heat dome, may shift slightly westward and cause temperatures to spike to record levels in Louisiana, Oklahoma and Texas. Georgia, however, will stay hot as well.
- Other cities that are forecast to see rare triple-digit heat include Tallahassee, Florida and Baton Rouge, Louisiana, along with the Gulfport-Biloxi region of Mississippi.
- Nashville and New Orleans are likely to come close to if not reach the 100-degree mark as well during the Wednesday through Saturday time frame.
- The National Weather Service forecast office in Tallahassee tweeted that the city could tie its hottest temperature on record, which is 105°F.
Threat level: Into the weekend, the heat will escalate in Texas, with highs across much of the state ranging from about 102 to 105°F. Given that the state is in a drought, the added heat will serve to dry out soils and vegetation even more, and contribute to elevated wildfire risks.
- Over the longer term, the relentless heat dome shows few if any signs of abating, instead it continues on its tour of the Lower 48 states, with extended forecasts favoring above-average temperatures across much of the country during the next two months.