Here's a bit of weather trivia for you: The record high temperature for July 6 was set in 1999.

It was 98 degrees.

That's nothing.

By Tuesday afternoon, 98 will likely sound positively, refreshingly cool to Lancaster County.

The thermometer is expected to top the 100-degree mark Tuesday, about 15 degrees above normal for this time of year, according to AccuWeather.

There's more bad news: It's going to actually feel hotter than that — possibly 104 or 105.

VIDEO: AccuWeather Forecast

"We're going to nudge just above the 100-degree mark, with the humidity measured in," said National Weather Service forecaster Barry Lambert.

Tuesday through Thursday will likely be some of the hottest days of the summer, with each day hitting the high 90s. Things will cool down — relatively speaking — to 92 on Friday and 87 on Saturday.

Until then, any advice for folks who have stuff to do outside?

"Don't do it," Lambert said. "Or at least they should not do it during the peak sun hours, if you can."

The National Weather Service has issued a heat advisory until 7 p.m. Tuesday. The agency recommends people drink plenty of non-alcoholic beverages whether they're thirsty or not and stay out of the sun in an air-conditioned or well-ventilated room.

If you must be outdoors, wear light-colored, lightweight and loose-fitting clothing.

The state Department of Environmental Protection, meantime, warned that the intense sunshine and high temperatures is causing ozone concentrations to rise to unhealthy levels.

The agency urged active children and adults, and particularly people with lung disease such as asthma, to reduce prolonged or heavy exertion outdoors.

Ground-level ozone, or smog, forms during summer months when nitrogen oxides from power plants and vehicles combine with organic compounds on extremely hot and sunny days.

It is a strong irritant to the eyes and upper respiratory system. Smog hampers breathing and damages crops and man-made materials such as monuments and statues, the DEP warned.

The lack of rainfall, meantime, has dried out lawns and shrubs, and there have been numerous reports of brush fires across the county in the past week.

U.S. Geological Survey data indicate that if things don't improve soon, the county could be put on a drought watch, which occurs when precipitation falls to 25 to 35 percent below historic averages.

"We're not quite there yet," Lambert said. "We'd need to have this dry spell extend a bit more. But this is the beginning of it. It's getting very dry out there."

During an average year, the county receives about 21 inches of precipitation during the first six months. So far in 2010, we've received about 18 inches.

tmurse@lnpnews.com