This summer's long-playing heat wave is beginning to rival the record scorcher year of 1980, causing 200 deaths across the nation, severely hurting agriculture and leading to a 22-percent increase in the cost of air conditioning.

Temperatures soared to 96 in Boston, breaking the record of 95 set in 1949 for the date. It was the 13th straight day of temperatures over 90 in Washington, short of the 20 consecutive over-90 days recorded in 1980. Similiar temperatures have been recorded on 27 of the past 38 days.

Here in Chicago, where the heat wave is blamed for the deaths of four patients in a nursing home with broken air conditioning, thermometers recorded the summer's 25th day of 90-degree or higher temperatures.

Although this summer's heat lags behind 1980 for records broken nationwide, national electric consumption figures compiled by the Edison Institute show that Americans actually have used more electricity this summer during the peak heat periods than three years ago.

The National Weather Service placed the cost of air conditioning for the United States in the last three weeks of July at $377 million, or 22 percent more than normal consumption. The weather service blamed the hot, humid weather that began in the Rocky Mountains early in July and spread across the country by the end of the month.

In Illinois, rising electricity consumption has cheered state and city budget officers because of local utility tax revenues, which rise when consumption goes up.

A. James Wagner, meteorologist with the prediction branch of the Weather Service's Climate Analysis Center in Washington, reported that the source of the discomfort lies thousands of feet up in the atmosphere and hundreds of miles to the north.

There, in the stratosphere, the jet stream has taken a more northerly route than usual, blocking out colder Canadian air that usually refreshes America's summers. The result has been to trap a mass of dense heated air over the mid-continent area, the so-called North American ridge.

Wagner said that within this vast formation, air is moving vertically between the Earth and the atmosphere, without much lateral movement. Heat has been intensified within the ridge.

Compounding the heating effect, he said, is the fact that the land across much of the Corn Belt is becoming parched. Since little moisture is left in the topsoil to evaporate under the sun's rays, fewer clouds develop, providing less shielding from the sun. Without evaporation, a process that cools the air, temperatures rise. This combination of factors has struck throughout the country in varying degrees.

An unusual feature of the heat this summer, Wagner said, has been its unsettled pattern: "the unusually strong high pressure in the upper air, milling around from week to week so that there have been records in different places." This has occurred mostly "in the central, north central and eastern regions of the U.S.," he said. "It changes weekly."

The forecast through the rest of August is not promising for any but utility tax collectors, it seems. Wagner said temperatures are expected to remain higher than average, "especially in the Midwest and Upper Mississippi Valley." He predicted generally dry conditions in the South, Southwest and Great Plains, and somewhat wetter weather in New England.

For Washington and vicinity, he said, aside from occasional local storms that may cool things a bit, it looks like more of the same through Labor Day.