State climatologist: past winter coldest in 35 years; 9th coldest on record
DES MOINES — A summary of the 2013/2014 winter season compiled by the state climatologist shows this past winter has been the coldest experienced in Iowa in 35 years and ranks as the ninth coldest winter in 141 years of records.
“It has certainly seemed like a long, cold winter and the numbers from our state climatologist’s office bear that out,” said Iowa Secretary of Agriculture Bill Northey, “Everyone is certainly looking forward to spring,”
“The meteorological season of winter runs from Dec. 1 through Feb. 28,” said Harry Hillaker, the state climatologist with the Iowa Department of Agriculture and Land Stewardship. “This past winter season has been the coldest experienced in Iowa in 35 years and ranks as the ninth coldest winter in 141 years of records. Temperatures this winter season averaged 14.7 degrees or 7.2 degrees below normal.”
On a month-by-month basis, all three winter months were unusually cold this past season:
• December 2013: 17.3 degrees; 6.7 degrees colder than average; 17th coldest December.
• January 2014: 13.9 degrees; 4.7 degrees colder than average; 35th coldest January.
• February 2014: 12.6 degrees; 10.5 degrees colder than average; 7th coldest February.
A colder December was last recorded in 2000, a colder January in 2010 and a colder February in 1979. Historically there have been only 24 winters among the past 141 seasons where all three winter months averaged colder than normal. Temperatures this winter have varied from about 10 degrees below normal in northeast Iowa to 4 degrees below normal over the southwest.
The cold has been very persistent this winter with nearly one-half (44) of all days averaging more than 10 degrees colder than normal while only four days averaged more than 10 degrees above normal.
Persistence has been the primary characteristic of the Iowa weather pattern this winter as there have been very few daily record low temperatures set. Elkader has recorded the lowest temperature of the winter with a minus 29 degree reading on the morning of Jan. 28. Slightly more than one-half of all Iowa winters have brought a lower statewide minimum temperature than the minus 29 recorded this winter.
A popular measure of cold weather is the number of days with temperatures falling to zero degrees or lower. The number of subzero days this winter (through March 7) have varied from 15 at Shenandoah to 50 at Decorah while typical seasonal totals vary from 10 to 30 days across Iowa.
Not only has the three mid-winter months been unusually cold, so was the late fall of 2013. The second one-half of October averaged 4.9 degrees colder than usual (coldest for the period since 2006). November 2013 averaged 2.9 degrees colder than normal (coldest since 2000).
Additionally, the first six days of March averaged 20.4 degrees colder than usual. It was the coldest start to March since 1962.
The persistent cold has allowed the soil to freeze to unusually great depths, despite abundant snowfall which acts to insulate the ground from the colder air above the snowpack. National Weather Service measurements indicate that soils under sod have frozen to a depth of about 2 to 3 feet while Iowa D.O.T. data shows the frost depth has extended as much as 5.5 feet beneath roadways.
The good news is that the depth of frozen ground has reached its maximum for the winter.
The thaw will primarily begin at the surface, but there likely also will be a very slow thaw at the base of the frozen soil layer. The best guess is that soils will be completely frost free by about April 10 statewide. Unusually warm and/or rainy weather would accelerate the rate of thaw while persistent cold or snow could delay the thaw even further.
While the cold has been very persistent and widespread over the winter, the amount of snow fall has been highly variable across Iowa. Snow totals so far this winter have been as much as 50 percent less than usual across portions of far western Iowa while the southeast corner of the state has seen about double the usual amounts.
County snowfall averages vary from 15 inches in Montgomery County of southwest Iowa to 57 inches in Fayette, Clayton and Buchanan counties of northeast Iowa. The statewide average snow fall stands at 36 inches and already exceeds the long-term average with about six weeks of the snow season remaining.
This marks the seventh snow season of the past eight with greater than normal snowfall. The long-term snowfall average is 31.0 inches.
What might be expect for spring weather after this long and cold winter?
The past two springs have brought an amazing variety of weather to Iowa. The spring of 2012 was the warmest of record in the state and unusually dry. Then in 2013, Iowa recorded a record wet spring along with near-record cold as well. The confidence with long-term weather outlooks is not very high. However, there is an expectation of mostly colder than normal weather for much of the remainder of March. It is worth noting that even a record-cold March would still be 8 degrees warmer than what was just experienced in February. The National Weather Service spring outlook also slightly favors below normal temperatures for the period through May. There is no strong indication for spring precipitation in 2014.
Additional information and maps on the winter weather can be found at www.IowaAgriculture.gov under “Hot Topics.”
Precipitation observers sought
Accurate flood forecasting, as well as drought assessments, depend upon reliable precipitation information. The State Climatologist Office of the Iowa Department of Agriculture & Land Stewardship, as well as the National Weather Service, encourage Iowans to become involved in a nationwide volunteer precipitation observation network known as the Community, Collaborative Rain, Hail and Snow Network.
This network was established in Fort Collins, Colo., in 1998 in response to a serious flood event and has spread to all 50 states and parts of Canada.
Iowa joined the CoCoRaHS network in July 2007.
There is no cost to join other than the need to obtain the standardized rain gage. Volunteer observers nationwide use 4-inch diameter plastic rain gages to insure uniform quality of observations.
Data is reported via the Internet and various other electronic options with data automatically archived and transmitted to the user community as soon as it is reported. All reporting details can be found on-line at www.cocorahs.org. Observers are needed statewide with particularly great needs in data-sparse portions of the state such as Adair, Adams, Cedar, Emmet, Keokuk, Louisa and Wapello counties.