Dangers of excessive heat are cumulative

If you feel like you’re taking a beating from the heat, you could be right. The effects of excessive heat are cumulative, and that makes a continued heat wave more dangerous as time goes by.

So you should check on senior citizens or others who may not have air conditioning, keep an eye on pets whose cooling systems are more easily taxed by the heat, and make sure you yourself drink lots of water and take lots of breaks if you must be out in the heat.

While a late afternoon thundershower cooled things off a little bit Friday afternoon, an excessive heat warning  continues to be in effect until 10 p.m. Saturday. The National Weather Service is predicting a high between 103 and 110 for the day and a heat index from 100 to 115.

The risk of heat exhaustion and heat stroke thus remains high and precautions should still be taken.

Avoid working during the heat of the day if you can.

If you must work outside, take plenty of breaks, preferably in an air-conditioned space or the shade. Drink plenty of fluids to remain hydrated and wear light-colored clothing to reflect the heat.

The hot, dry weather conditions have also increased the risk of fire. Scattered thunderstorms are not enough to eliminate the hazard. People should continue to be extremely cautious with barbecue pits, fireworks, open flames of any kind or sparks from any source. The low relative humidity combined with high temperatures is highly favorable to rapidly spreading grass and brush fires.

St. Francois County Sheriff Dan Bullock noted that a fire started last weekend in the Parkland just from a spark while brush hogging. “One spark, that’s all it takes,” he said. He added that the brief thundershowers have not really alleviated the danger.

Although the county has no legal authority to issue a burning ban, Bullock and county officials have pleaded publicly for all county residents to avoid open burning until further notice.

Cigarette butts in particular should not be thrown down on the ground. The grass is dry and makes perfect tinder to start a fire.

A cigarette carelessly thrown down at the Bonne Terre Memorial Library ignited the mulch there and scorched the side of the building. Fortunately it was quickly noticed and extinguished, or the damage could have been greater.

 In Iron County, officials had thought a cigarette might have started a fire in the Mark Twain National Forest that burned as many as 600 acres. However, officials now think it may have been a set fire that got out of control.

Conditions being so dry, the blaze fueled a wildefire of the type normally seen only out west. Roads presented no barrier to the spreading fire, it simply jumped from tree top to tree top. Fortunately, that area is much less populated than St. Francois County, but many acres of forest were still destroyed before the fire could be contained.

This year has been one of the hottest on record. The National Oceanic and Atmospheric Administration reports that 40,000 daily heat records have been set so far this year. That compares with 25,000 daily heat records set last year by this date. Last year was the 9th warmest on record.

Heat waves are not too unusual in summer, of course. High-pressure systems put the smack down on the country all the time, and the Midwest is often right at the center.

Weatherwise what happens is that the polar jet stream meekly recedes into Canada, inviting higher pressure systems to come on over and sit for a spell. Within such a system, the denser air will sink and become even warmer. And, since warmer air can hold more water than cooler air, there is usually also relatively high humidity.

The high humidity will the drive the heat index far higher than the actual temperature, but that’s one of the unusual things about the high pressure system this time. Not only has it been a little bit early, it’s been very, very dry. The heat index has been staying at or below the actual temperature.

“In the last couple months, it hasn’t rained much,” explained Ben Miller, a meteorologist with the National Weather Service, “so we’ve been kind of living off only the moisture from spring, and that’s pretty much gone.”

With winter conditions having been dryer than usual, the spring rains alone haven’t been enough to fuel much humidity. That’s good in the sense that it doesn’t feel quite as hot as it really is, but it’s also helping fuel this record rise in temperatures.

“It takes more energy to heat water in the air than if there is less water in the air,” Miller explained. “If there were more humidity, the temperature wouldn’t be able to rise as high.”

This particular high pressure system has also been unusually early, and unusually broad, driving record highs throughout the nation.

Is it part of global warming?

Although climate models for global warming do predict more of these kinds of weather patterns, it is too early to say whether this is part of such a pattern, Miller said.

Until many summers go by and a definite warming trend is established, it can’t be determined whether this data point is truly part of global warming or just a fluke.

“You can’t correlate a particular weather event with it,” he explained. “It may very well be connected, but it’s too early to make assumptions.”

There are no official climate stations in St. Francois County to know for certain if a record high was set in our county, but Miller said record highs have been set at official weather reporting stations throughout the region.

St. Louis is the nearest weather reporting station, and recorded an all-time high when it hit 108.

Miller advised people to be mindful of the heat and take extra precautions.

“Be careful out there,” he said. “Take lots of breaks, drink water, wear light clothing, avoid the heat of the day.”

Renée Jean can be reached at 573-431-2010, ext. 117 or at rjean@dailyjournalonline.com.