By James B. Kelleher and Julie Ingwersen
CHICAGO (Reuters) - Much of the United States basked in another day of unseasonably warm weather on Tuesday as one of the mildest winters on record gave way to a balmy spring and possibly a hot summer that could cause difficulties for crops.
On what meteorologists consider the first day of spring, record highs were set in dozens of central and eastern cities, from International Falls, Minnesota on the Canadian border to Lexington, Kentucky in the south, according to the National Weather Service.
In Chicago, the high at O'Hare International Airport reached 85 degrees Fahrenheit (29.5 Celsius), smashing the previous record of 76 degrees (24.5 Celsius) set in 1921, according to Accuweather.com.
It was the sixth day in the past seven that temperatures in Chicago reached 80 degrees (26.5 Celsius) or more. Brian Edwards, a meteorologist at AccuWeather.com, said the warmth was likely to linger into next week across much of the country.
"It looks like things will continue like this for several more days and then trend downward a little bit as we go into the weekend," Edwards said. "But even next week, temperatures will still be well above normal."
The warm weather blanketed the "Corn Belt", which stretches from Ohio in the east to Nebraska in the west and where the traditional start of planting begins in less than two weeks.
Current conditions would be ideal for farmers getting their seed in. But they have also raised concern that the unusually warm winter could give way to a hot, dry summer bad for crops.
Iowa, the No. 1 corn state, is on track to have its warmest March ever, according to Harry Hillaker of the Iowa Department of Agriculture.
But a study released this month by the University of Illinois found that warmer-than-normal winters were usually followed by average summer temperatures. Hillaker said a study of the data showed that "what goes on in March oftentimes doesn't continue to the late spring and early summer".
He said the main risk now was farmers growing horticultural-type crops such as apples and grapes, which were "definitely being fooled, big-time, by this long spell of warm weather".
DANGER OF SEASONAL FREEZE
Warm temperatures have left fruit trees and vines "very susceptible" to a seasonal freeze that would kill blossoms.
Some private meteorologists and forecasters are worried the warm winter portends a summer difficult for crops and farmers.
Craig Solberg, senior meteorologist with Freese-Notis Weather Service, said that except for 1992 -- a warm winter followed by a very cool summer due to the eruption of Mount Pinatubo in the Philippines -- the 10 warmest winters on record have been followed by warmer-than-normal summers nationwide.
On the West Coast, warm temperatures returned to most areas after a weekend winter storm that closed highways and was blamed for two deaths in the Sierra Nevada mountains.
But rain and cool temperatures persisted in the Pacific Northwest and storm warnings remained in effect for several mountain regions.
The National Weather Service also issued flash flood warnings for portions of Texas, Oklahoma, Arkansas and Louisiana as a strong storm passed slowly over the region. South and central Texas remain in the grip of a drought that began early in 2011 and developed into the state's worst one-year drought.
(Additional reporting by Christine Stebbins and Jim Forsyth; Editing by Greg McCune and Ron Popeski)