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SALT LAKE CITY — Last month was Salt Lake City's warmest May on record, according to National Weather Service data, reversing a cold trend during the first third of the year.
The average temperature at the weather service's Salt Lake City International Airport station ended up at 67.2 degrees, breaking the previous record of 66.7 degrees set in 1934, according to the agency's climate records. The final average was also 5.7 degrees above the 30-year normal of 61.5 degrees.
The National Weather Service's Salt Lake City records date back to 1874.
The National Centers for Environmental Information is expected to release more statewide data next week, though preliminary numbers show that May produced above-normal temperatures across most of the state — though, not all were as above normal as Salt Lake City. For example, Cedar City's average temperature of 58.4 degrees ended up 2 degrees above normal.
It's the exact opposite of the first third of the year, which was one of the colder starts to a year in recent memory. The agency, which compiles weather service data across the state, lists Utah's average temperature from Jan. 1 to April 30 as 32.3 degrees, which is 2.3 degrees below the 20th-century normal and the 21st coldest first four months to a year since at least 1895.
The cold start had much to do with a consistent pattern that sent storm after storm toward Utah, which is also how the state ended up with a record snowpack. It didn't allow for many high-pressure systems to develop over the state to warm things up.
A new "anomalous" pattern developed through most of May that changed things up, says Glen Merrill, meteorologist and hydrologist for the National Weather Service.
He explains that May is typically a "roller coaster" month in Utah. It's known to be consistently inconsistent, bringing a mixture of high-pressure systems that can boost temperatures into the 90s across the Wasatch Front only to be cooled down by a storm system that could even bring snow to the valleys.
But this year, high-pressure systems began to build up over the northern Rocky Mountain region while low-pressure systems developed southeast of Utah, creating what's known as a blocking pattern that pulled moisture from the Pacific and warm air from areas south of Utah. The dominant pattern kept temperatures generally warmer than average throughout the month, with very few extremes.
"What we've seen is consistent weather nearly on a daily basis with minimal fluctuation holding in the 70s and the low-80s for weeks now," he told KSL.com Thursday morning, noting that the consistency was abnormal.
In the end, Salt Lake City ended up with above-normal average temperatures during 26 of the 31 days in May, though it didn't hit the same extremes as the previous record in 1934, which remains the hottest year on record in Utah's history. The average maximum temperature reached 82.4 degrees that year, 1.9 degrees above the second-highest May maximum average, 3.9 degrees above the average maximum this year and nearly 10 degrees above the city's current normal.
The weather patterns that developed in May also show no sign of stopping anytime soon at the beginning of meteorological summer. Merrill says don't be surprised if the warm temperatures and scattered showers and thunderstorms remain in place through at least the next two weeks.
"We're just kind of locked in this (pattern)," he said. "Call it rinse and repeat."
