The eastern and mid-Atlantic states continued to sizzle yesterday under stifling temperatures, but forecasters had one tidbit of good news for the heat-weary.

"Some relief is on the way," said Walt Zaleski, a meteorologist in the National Weather Service's southern regional headquarters.

While much of the country remained under a Weather Service excessive-heat warning or watch, a strong cold front started blowing down from Canada, moving southeastward across the United States and cooling down much of the Rocky Mountain region and the central plains, Zaleski said.

The deadly heat wave that embraced the Southwest for most of this month and had recently moved into the midsection of the country succumbed to the front.

Tucson cooled to 98 degrees on Monday, ending the city's record 39-day string of temperatures reaching 100 degrees or higher. Denver, which reached a record-breaking 105 degrees on July 20, was down to 65 degrees yesterday. Las Vegas, which tied its 117-degree record temperature on July 19, was back to its normal mid-summer range of 100-to-105-degree highs. And 90-degree temperatures in Kansas gave way to the high sixties and low seventies.

Seasonal temperatures were predicted nationwide through the weekend.

"Oh, it's going to be dramatic, dramatic," said Bruce Terry, a meteorologist in the National Weather Service's Climate Prediction Center in Camp Springs, Md. "When it goes through, you'll know it for sure."

But forecasters said that by the beginning of next week, another ridge of high pressure could build up across the Rockies, trapping hot air across the region and making temperatures soar again in the West.

That is the last thing Arizona officials want to hear. The state, reeling from 27 deaths presumed to be heat-related so far this year, is on its way to breaking its hyperthermia record, said Will Humble, bureau chief for disease control in the state's department of health services. Most of the 24 deaths this month in the Phoenix area were homeless men. The tally does not include immigrants who die of dehydration or hyperthermia while trying to walk across the desert into Arizona from Mexico, Humble said.

"It stays hot all the way through September, so we've got a long way to go," Humble said.

While 100-degree-plus days are commonplace in the West and Southwest, the mid-Atlantic is not accustomed to such extended hot spells. In Raleigh, N.C., shelters displayed white flags to signal they were open as the heat index exceeded 100 degrees.

Special correspondent Caroline Keating contributed to this report.