Published: Wednesday, Aug. 8 1990 12:00 a.m. MDT

THIS SUMMER'S been a scorcher so far, hasn't it - and again this week the mercury is flirting with the 100-degree mark. Hot? Want to cool off? How about a visit to the coldest spot in Utah.

Peter Sinks, an uninhabited portion of Logan Canyon, five miles west of the Bear Lake summit overlook, holds the honor of producing the Beehive State's all-time coldest temperature - 69 degrees below zero - on Feb. 1, 1985. The spot is also shown on maps and guides as Peter Sink and Peter's Sink.(If you want to visit Utah's coldest occupied area, try Woodruff, a town 35 miles southeast of Peter Sinks. The temperature there dropped to minus 50 degrees on Feb. 6, 1899, the state's coldest reading before temperatures at Peter Sinks were measured. In contrast, Utah's hot spot is St. George, where the temperature hit a record 116 degrees on June 28, 1892.)

The phenomenon of Peter Sinks raises all kinds of questions. . . .Why do temperatures drop so low at Peter Sinks?

According to William J. Alder, meteorologist in charge of the Salt Lake office of the National Weather Service, Peter Sinks records especially low temperatures because of the surrounding terrain, which adds to the effect of long winter nights in which considerable cooling occurs as the heat escapes upward. After all, cold can be defined as simply the absence of heat.

Zane Stephens, who works for the state climatology office in Logan and is one of the two young weather wizards who discovered the cold in Peter Sinks about eight years ago, said the sinks are part of a two-fault system at the top of Logan Canyon. Water eroded the area's underground limestone rocks and eventually created caves and caverns. When they finally collapsed, the sinks were created.

Peter Sinks is a tub-shaped valley about a mile long and three-quarters of a mile wide. Stephens, also a TV weather correspondent for Logan, added that the combination of a temperature inversion, a good snowpack, a cold air mass and no wind are needed to make Peter Sinks extremely cold.

He said Peter Sinks actually dams cold air in its tub-shaped valley because the cold air is so dense and heavy. In areas like Peter or Middle sinks, the temperature can be 15 to 20 degrees colder at the bottom than the top. Stephens said he's discovered that in such sinks observers notice the air temperature can drop 10 to 15 degrees just by taking several footsteps downward. He's felt cold air leaking out of the bottom of Middle Sinks, a phenomenon not unlike a dam of water that overflows. Don't other places in Utah, like the top of Timpanogos Peak or Kings Peak, actually get colder than Peter Sinks?

Alder said there might be such places. However, these are not regularly measured, and it would be unrealistic to measure temperatures in every single area of the state at all times, especially in the winter.

The wind-chill factors might be three figures of sub-zero on high places like Timpanogos, but unfortunately wind does not count toward official cold temperatures. (Stephens said Logan has experienced chill factors of 100 degrees below zero in the past.)

Peter Sinks' terrain is not unique, and Alder speculated that other similar sites with extreme coldness could surely be found in the Rockies.

Stephens said Montana's Rogers Pass, between Missoula and Helena, which is not an area of sinks, is the nation's coldest official spot. Middle Sinks, just southwest of the Logan Canyon summit, is the nation's third-coldest spot - only 3 to 4 degrees warmer than No. 2 Peter Sinks, about four miles to the west.Is Peter Sinks, at an elevation of 8,100 feet, also the coldest spot in Utah during the summer?

"I suppose it could be. At least it's one of the coldest," Alder said.

"It's definitely one of the coldest spots in the state, period," Stephens said. He said temperatures usually drop into 20s and 30s at night in the summer and sometimes as low as the teens.

Stephens said Peter Sinks is a rather cool area just about any time of the day or year, and when conditions with no wind occur, it really cools off.How hot does Peter Sinks get in the summer?

Stephens said no instruments operate in Peter Sinks during the summer, but he had a thermometer there a few summers ago and the temperature hit 84 when it was 99 in Logan and 100-plus in Salt Lake City.How much annual precipitation does Peter Sinks get?

Temperature readings have received most of the emphasis at Peter Sinks, so precipitation estimates must come from nearby Tony Grove. This site received 34 inches of water from October through June. Annually, the area receives about 40 inches of water. This obviously translates into a lot of snow.How was Peter Sinks selected as a weather station site?

Stephens said that in the fall of 1982, he and a friend from Salt Lake City, Mike Boman, who worked for TV weatherman Mark Eubank, wanted to find a cold location in Utah that no one had ever checked for temperatures.

"It started out as just fun, to find the coldest spot in Utah," Stephens said.

First, they checked the Dry Lake area in Sardine Canyon. The temperature reached 30 below zero there during a fairly mild winter.

Later they stumbled across some European weather information that noted the unusually cold temperatures in sinks areas. So, they went to the Middle Sinks area at the top of Logan Canyon. That later led to spotting Peter Sinks on the map, theoretically an even colder spot for frigid temperatures.

Stephens said trees can't survive where the air temperature falls below minus 50 degrees. Hence there are no trees and very little vegetation in the sinks. This is a "reverse timberline" phenomenon.

(Additional information)

A Peter Sinks miscellany

- Snowmobilers sometimes visit the area in the winter and hunters during the fall deer hunt. Otherwise, it's a difficult, remote location to find since no name marker is there.

- Zane Stephens, who co-discovered Peter Sinks' meteorological quirks, says the thermometer that recorded the state's all-time low temperature was broken by vandals a few years ago and that he just has a piece of it left as a souvenir.

- Some thermometers have frozen while trying to measure the extreme cold in the Logan sinks areas.

- Stephens said the recent drought years have lessened snowpack in the Peter Sinks area and that, coupled with no real arctic blasts of cold air, has meant the temperature fell below minus 50 only once all last winter.

- Fog is rare, but it does occasionally occur in the sinks areas.

- The sinks are still sinking, and as they become deeper, temperatures may become colder.

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