The weather forecast called for clear skies and a low temperature of 21 degrees. A typical winter morning across much of the United States, right? Not quite. That was the prediction for Aug. 13 and 16, 1993, at Truckee, one of the coldest towns in the contiguous 48 states. That year, Truckee recorded the nation’s lowest temperature 62 out of 365 days, more than any other community in the lower 48. The average minimum temperature at the Truckee-Tahoe Airport for July and August in 1993 was a nippy 31 degrees, nearly 7 degrees below normal.
Read Mark’s story on the Snowiest places in California
Climatologists blamed the unusually chilly temperatures on the violent 1991 eruption of Mount Pinatubo, a volcano in the Philippines. That blast, the most powerful in a century, spewed 20 million tons of volcanic debris more than 15 miles into the atmosphere. Stratospheric winds distributed these materials and sulfur aerosols around the globe, where they remained suspended in the upper atmosphere, reflecting incoming solar energy back into space and cooling the planet. The Pinatubo event may likely have contributed to Truckee placing first in the coldest in the nation competition not only in 1993 but also in 1991 and 1994 also.
Out of the nearly 8,000 reporting weather stations in the U.S., Truckee frequently registers the lowest daily temperature in the nation.
The Pinatubo eruption chilled the average global temperature to its lowest level since the early 1920s. Within two years, the atmospheric cooling induced by this volcano nearly matched the entire global warming of the last 100 years. Even without massive volcanic eruptions disrupting worldwide temperatures, during the summer months Truckee ranks as one of the coldest locations in the country, excluding Alaska. Out of the nearly 8,000 reporting weather stations in the U.S., Truckee frequently registers the lowest daily temperature in the nation. Perhaps counterintuitively, these national lows don’t happen during the winter ski season as one might expect. The crisp temperatures are more noteworthy because they occur from June through early October, when residents and visitors are more interested in warm weather sports like golf, boating and fishing.
For more than 20 years during the 1980s and 90s, Dr. David H. Hickcox, a geography professor now retired from Ohio Wesleyan University, compiled the daily temperature extremes in the United States. For nearly all those years, Truckee ranked in the top 10, and usually in the top 5 for cumulative national low temperatures. Dr. Hickcox’s selected criteria for cold spot status did not pertain to a community’s annual average temperature (climate); rather it was determined by tallying up the number of days per year any given location recorded the lowest or highest temperature in the nation. In that category, Truckee was a regular contender. Other regional players are Mammoth Lakes, Boca Reservoir, Olympic Valley and the undisputed champ – Bodie.
Similar to frosty spots like Stanley, Idaho, West Yellowstone, Mont., and Gunnison, Colo., altitude and topography are primary factors in Truckee’s elite status as a nationally recognized cold spot. Located at the Truckee-Tahoe Airport, the official National Weather Service thermometer is 5,900 feet above sea level. Since the atmosphere cools at an average rate of about 3.5 degrees Fahrenheit for every 1,000 feet gained in elevation, Truckee’s average low temperatures are about 20 degrees cooler than sea level locations.
Topography also plays a vital role in this equation. At night, cool air from high mountains surrounding the airport sinks downslope and pools in the Martis Valley, a high-elevation basin where the airport is located. The cold dense air settles and creates a chilled microclimate. The airport thermometer is located within this sink, which contributes significantly to Truckee’s low readings. In fact, due to this atmospheric inversion, morning temperatures at the Truckee-Tahoe Airport are often significantly lower than Donner Pass at 7,000 feet.
High pressure tends to dominate West Coast weather during the summer and fall. This large, semi-stationary air mass forces storms far to the north, reducing wind and stifling the atmospheric mixing that raises overnight surface temperatures. Stagnant air does not disturb the cold pool trapped in the basin. In addition, air under the dome of high pressure contains little moisture. With low levels of humidity there is no water vapor to trap and hold the sun’s daytime heat. As soon as the sun sets, temperatures plummet. The same principle applies to arid deserts, known for scorching heat during the day followed by frigid nights. Truckee’s average minimal morning temperatures near the airport range in the upper 30s during summer.
Another component that contributes to Truckee’s extreme temperature fluctuations is its distance from any large body of water. Oceans and large lakes like Lake Tahoe, heat up and cool off slowly while land surfaces gain and lose heat more rapidly. Truckee’s afternoon temperatures are usually significantly warmer than those recorded at Tahoe City, but at night plunge quickly and are usually at least 10 degrees colder by sunrise. Truckee’s temperatures may be chilly on early summer mornings, but the town’s reputation as a cold spot is considered a tongue-in-cheek joke among those who enjoy the region’s relatively balmy winters. Situated just 200 miles downstream from the Pacific Ocean, average temperatures in the Tahoe Sierra, particularly during winter, are much milder than the real cold spots in the Rockies and Northern Plains.
In the final years of his extreme temperature competition, Dr. Hickcox decided to mix it up a bit. In 1999, the criteria were changed to include data from small hamlets with populations of 100 people or less, as well as remote automated recording stations, many of them located in high-altitude basins. The National Weather Service only considers towns with a minimum of 2,500 inhabitants in their daily survey of the nation’s highest and lowest temperatures. The new rules pushed Truckee and other top tier cold spots to the margins and a new No. 1 emerged.
The abandoned ghost town of Bodie, situated in a sink at 8,300, perennially ranks as the No. 1 location in the U.S. with the most daily lows. In 2001, rangers at Bodie reported the coldest temperature in the country on 167 days, which blew away all competition nationwide. In contrast, Truckee’s greatest total of daily low temperatures was just 62 in 1993.
But Truckee has another claim to fame that hasn’t changed. According to the Western Regional Climate Center in Reno, it is among the snowiest places in the country, ranking third among western communities with an average annual snowfall of 207 inches — just 3 inches shy of Mammoth Lakes. In his 2007 book, “Extreme Weather: A Guide and Record Book,” Christopher Burt ranks Truckee as the snowiest town in the U.S. with a population more than 10,000.
