A dangerous and record-challenging heat wave will affect much of the East this week as a once-delightful air mass turns ugly.

In some locations this heat wave will rival many that have occurred in the past 20 years with the potential for up to a several-day stretch of temperatures in the upper 90s to low 100s from southern New England to the Carolinas.

Cities from Hartford, New York and Philadelphia to Washington, D.C., Raleigh and Columbia will swelter.

Temperatures over the Independence Day were just a warm up compared to how nasty the weather will get, especially for those who do not have air conditioning or must do manual labor outdoors.

The highest temperatures will occur Tuesday and Wednesday in northern areas, while southern locations feel the inferno later in the week.

While highs in the lower 90s with humid conditions are a common occurrence in the South, even many Southerners get uncomfortable when high temperatures rocket into the upper 90s.

The massive high pressure area that had its origins in central Canada is being worked over by intense July sunshine over the eastern U.S. Locations that experienced record-challenging lows will be facing record-challenging highs.

Humidity levels will continue to lag with this heat wave to start the week. However, the humidity will slowly climb as the week progresses. Even as actual temperatures throttle back in northern areas, higher humidity levels could drive AccuWeather.com RealFeel;® temperatures even higher.

A heat wave is generally considered by meteorologists to be any three-day stretch or more of 90-degree or higher temperatures, with or with out high humidity. Heat waves are uncommon in northern, coastal areas. The heat wave will be felt even on many beaches in the Northeast this time.

In New York City, according to the National Weather Service, the granddaddy of all heat waves occurred in late August into early September during 1953, when temperatures hit 90 or higher on 12 consecutive days. The blast furnace included two days of temperatures with 100 degrees or higher.

The heat wave just now beginning could last for seven days or more and would be one of the worst, early-summer heat waves on record.

This accomplishment would fit in well with happenings this year. In many areas from the Tennessee Valley to the mid-Atlantic, we have had one of the warmest springs on record. The warmth has accelerated growth of fruits and vegetables.

In parts of the Northeast, strawberries were harvested in during May instead of June, while peaches are also also being picked a month ahead of schedule.

People are urged to avoid the hot sun and strenuous activities during the midday and afternoon hours in this heat wave. Heat stroke and Hyperthermia rank near the top of weather-related deaths in the U.S. annually. Be sure to drink plenty of liquids and try to keep cool as much as possible.

(Source: Accuweather.com)