Ask Mr. Answer Person: "Why does the problem of broken water lines and mains get worse as the weather starts to warm?"

(Jane asks:  I have often heard that, as the weather starts to warm, the frost in the ground goes down causing more broken water or sewer lines.  Is it true?   Does not make sense to me.)

Mr. Answer Person says, "It doesn't make sense to me, either.  That's why we turned to the Iowan who is most knowledgeable about our weather--State Climatologist Harry Hillaker.  Here's what he had to say:

"There are many factors impacting frost depth.  Obviously the largest one is the air temperature.   We've had unusually cold weather since mid-October with the state as a whole recording the coldest winter-to-date since the 1978-1979 season.

Generally frost will continue to go deeper into the soil as long as the air temperature is averaging below freezing.   Thus, even though we are well past the typical coldest part of the winter the long-term average date for daily mean temperatures to climb above freezing in Northeast Iowa is not until March 18th.   Thus, we could see frost depths continue to go deeper for some time yet (though not nearly as quickly as would have been the case earlier in the winter.

Other factors for the extent of frozen soil are snow cover and soil moisture.   The drier the soil, the more quickly it can cool.   We came into the winter with soils in northeast Iowa a little drier than usual, thus this relative dryness would be a small factor in the deeper than usual frost.   Snow is an excellent insulator.   Thus, a deep snow cover usually inhibits a deep penetration of frost as the snow insulates the relatively warm soil from the much colder air above the snowpack.   Decorah has had a fairly deep snow cover since mid-December.   However, temperatures were unusually cold prior to the snowpack becoming established.   There were roughly 18 days with daytime maximum temperatures being below freezing before a snow cover was established.

Also, snow cover is not a factor for roadways and areas where snow is regularly removed.   Thus, regardless of how much snow falls the areas under pavement typically are completed exposed to cold air, and thus will see deeper frost penetration than areas beneath undisturbed ground."

(Our thanks to State Climatologist Harry Hillaker for being "Mr. Answer Person" for this question)