It really is that hot because of the humidity

This week just seems like such a fitting time to answer this one:

Q: I understand the notion of the wind-chill factor in the winter. It’s the actual temperature, plus how much colder the wind makes it feel. But I don’t understand heat index. It seems like if it feels that hot, it’s that hot and should be the temperature. What is the difference?

A: According to the National Weather Service, there is a very simple formula for calculating heat index.

In fact, here it is, straight from the service: HI = -42.379 + 2.04901523T + 10.14333127R - 0.22475541TR - 6.83783x10 -3 T 2 - 5.481717x10 -2 R 2 + 1.22874x10 -3 T 2R + 8.5282x10 -4 TR 2 - 1.99x10 -6 T 2 R 2.

OK, so it’s not so simple. About the only thing I connected with in that entire formula is, at the very end, it came close to spelling out R2-D2.

If you’re one of those people who understands mathematics better than I do (we’ll refer to this group as “Everyone Above Age 11”), you might want to figure out the formula. If so, the “HI” stands for heat index, “T” stands for temperature and “R” is for relative humidity.

The weather service also gives a good, easy-to-understand description of heat index. This is straight from one of the service’s Web sites: “Our bodies dissipate heat by varying the rate and depth of blood circulation, by losing water through the skin and sweat glands and as a last resort, by panting, when blood is heated above 98.6°F.”

Sweating cools the body through evaporating the heat from the body. High relative humidity reduces that evaporation, however, which reduces the body’s ability to cool itself.

One other thing the weather service says is if the heat index is 105 to 129 degrees, you are likely to experience sunstroke, muscle cramps and/or heat exhaustion if you insist on staying outdoors.

Q: Which am I supposed to believe? Is it cheaper to use your stove or is it cheaper to use your microwave to save electricity?

A: This is an intriguing question. I’m still looking for a basic answer. By that, I mean, if you have, say, a frozen meal and the package gives microwave directions and oven directions, which would take more energy.

I’m determined to find that answer.

Meanwhile, I have come across this information from the U.S. Energy Information Administration:

There are 92.1 million microwave ovens in U.S. households. They account for 1.7 percent of all annual electricity consumption (19.3 billion kilowatt hours).

There are 59.7 million range tops, which account for 2.8 percent of consumption (32 billion kilowatt hours).

There are 47.8 million ovens, which account for 1.8 percent of consumption (21 billion kilowatt hours).

Along those lines, I have heard that the clock on a microwave accounts for about half or more of the microwave’s total energy consumption. If anyone knows whether that’s true, let me know. Meanwhile, I’ll look into it, as well.

Staff Writer Bernie Delinski writes Just Ask, which runs Wednesdays in the TimesDaily. If you’ve got a question, e-mail it to justask@timesdaily.com, fax it to 740-4717 or send it to Just Ask, c/o TimesDaily, P.O. Box 797, Florence, AL 35631. Include your name and contact information.