Today and tomorrow look like the worst days in what promises to be a long, hot and miserable week in the Land of Pleasant Living. The forecast shows highs in the 90s every day, all week, with plenty of humidity in the air. Relief in the form of a cool front from Canada may stall to our north.

A heat advisory has been posted for today, extending into the evening. And it's likely to be posted again tomorrow. With high humidity, the heat index - really the "misery" index - is expected to climb to 105 degrees. That's what it "feels" like, because high humidity slows our body's ability to cool itself by sweating. That sweat has to evaporate to have its cooling effect, and that's more difficult when the atmosphere is already loaded with moisture.

After tomorrow, things will "cool" a bit. But the humidity will remain high, so it will continue to feel very uncomfortable. And as the heat wave continues, even though daily highs are a bit lower, homes and workplaces that were bearable in the early days of the Big Heat will become less so. Vulnerable populations will begin to be seriously distressed and ill.

The demand for power to run fans and air conditioners will also go up as this heat wave lengthens. Public utilities will come under more stress, especially in light of the the fact that this heat wave is not limited to one region of the country. Twenty-one states yesterday reported at least one station with highs of 100 degrees or more. Forty-seven states hit 90 or more. This heat is cooking almost everybody from L.A. to GA. So power-sharing will be difficult. I would not be surprised to see brownouts somewhere in the East by week's end.

And, we can expect the air quality to deteriorate in the high heat. You can monitor just how bad it's getting by clicking here, and then on the map point closest to the city you're interested in. For Baltimore, click here.

None of this should come as a complete surprise. This is, after all, the hottest week of the year in Baltimore, on average. See Friday's post.