Sweltering heat continues to bake much of central, eastern Lower 48

WEATHER NEWS: Sweltering heat continues to bake much of central, eastern Lower 48

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A significant heat dome has been crowding weather maps over the Lower 48 states for the past week, bringing blistering temperatures that have toppled records. Highs have spiked 10 to 20 degrees above average in spots, and some places have endured their hottest and most humid weather ever observed during June.

Now the heat dome is languishing over the Tennessee Valley and bringing highs of 95 to 100 degrees from the Corn Belt to the Carolinas, with exceptional humidity in the Midwest exacerbating just how sultry it feels. High humidity levels are contributing to heat index values pushing 115 degrees in spots.

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Because of the punishing combination of heat and humidity, more than 95 million Americans are under excessive heat warnings or heat advisories from the Florida Panhandle to northern Michigan.

Record-challenging highs are predicted Wednesday in Detroit, Chicago, Indianapolis, Columbus, Knoxville and Atlanta.

A new pulse of heat, meanwhile, is on the horizon and looks to become established into early next week. There are signs that the anomalously toasty temperatures could linger seven to 10 days or more, taking a toll on heat-stressed residents.

Since the weekend, heat has expanded north and east while withdrawing from California and the Southwest, leading to a slew of record temperatures from the Plains to the Southeast. The ongoing episode is impressive not just for its exceptional daytime highs, but associated elevated nighttime lows and saunalike humidity.

Here are a few of the more notable records collected from just the past two days:

  • St. Louis had its warmest overnight low on record for June on Monday night into Tuesday morning. Temperatures didn’t dip below 83 degrees. A daily record warm minimum also was set Wednesday morning with a low of 81 degrees. St. Louis also hit 100 degrees on Monday, edging out the record of 98 set in 1952. Another record was snagged Tuesday with a high of 98 degrees.
  • Kansas City, Mo., had a morning low of 81 degrees on Monday, which was the warmest in nearly 16 years there. At 4 a.m. on Monday, the heat index was still 92 degrees.
  • Chicago (Midway International Airport) managed a high of 100 degrees on Tuesday, the earliest in the year it has hit the triple digits since 2012. The average high there in mid-June is 80 degrees.
  • Milwaukee experienced its highest heat index in June since 1948. It reached 109 degrees at 3:52 p.m. Tuesday, tweeted the Maxar Weather Desk, the product of a 98-degree temperature and 73-degree dew point.
  • Columbus, Ohio, recorded an unprecedented dew point, which is a measure of humidity, of 84 degrees at 6:45 p.m. on Tuesday. Any dew point over 80 degrees is exceptionally sultry. According to the National Weather Service in Wilmington, Ohio, that dew point beat the previous record high by 3 degrees. Columbus also posted a heat index of 115 degrees on Tuesday — among its highest on record.
  • Dodge City, Kan., posted a low temperature of just 83 degrees on Monday, its warmest minimum temperature ever observed in any month of the year.
  • North Platte, Neb., soared to 108 on Monday, its highest June temperature on record.
  • Additional records: Columbia, S.C., hit 103 degrees on Monday. Madison, Wis., set a record high of 96 on Tuesday. Nashville managed a 97-degree high on both Monday and Tuesday, tying one record and breaking another. The Music City also had a record-warm low on Tuesday morning at 81 degrees.

The record-setting warm overnight low temperatures, of which there have been many, are potentially even more dangerous than daytime highs. While groups vulnerable to heat may be able to escape to air-conditioned public environment like a mall, shopping complex, library or public cooling during the day, they may not have access to cooling at night. That is especially true for those in challenging financial situations.

When overnight temperatures remain hot, the human body is deprived of its natural cool-down window and doesn’t have an opportunity to reset before daytime heat returns. That accumulated heat stress can be deadly for vulnerable individuals.

Before the heat spread into the central and eastern states, a slew of records occurred last week and over the weekend from Texas to California’s Central Valley. Death Valley, Calif., soared to 123 degrees on Friday while, over the weekend, Phoenix hit 114 and Las Vegas climbed to 109. Weekend highs peaked at 105 degrees in Austin and San Antonio.

Dozens of other records are in jeopardy Wednesday, with triple-digit heat expected in Atlanta and Columbia, S.C., while Chicago is predicted to soar into the mid- to upper- 90s. Nashville could flirt with 100 degrees, and mid- to upper-90s are likely virtually everywhere across the South.

The heat is forecast to continue Thursday, with Nashville around 100, northern Florida in the upper 90s, southwest Kansas in the lower 100s; and Houston with a high around 98.

A cold front will bring some relief to the Upper Midwest, Great Lakes and Ohio Valley on Thursday, along with the chance of some severe thunderstorms. But, by Friday, the next wave of heat will be building back to the northwest with temperatures in the 90s expanding into Montana.

The heat dome is predicted to intensify again over the weekend in the Central states, bringing a surge of record-challenging high temperatures to the central and northern Plains. By early to the middle of next week, the excessive heat will be on the move toward the Upper Midwest and Ohio Valley, and possibly the East Coast.

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