Warming up to weird weather As Chicago finally heats up, some experts point to altered jet stream and effects of climate change

Chicago started the year in the midst of a record stretch of 335 days without an inch or more of snow. Then we had the wettest April on record. Cold and wet weather in spring and early summer flooded homes, postponed baseball games and disrupted concerts and barbecues. July brought warm and dry weather, with exceptions — particularly one day late in the month when we exchanged T-shirts for sweatshirts. Then August started cooler than normal, with a hint last week of autumn.
"Worst. Summer. Ever," Shtulman wrote early this month in an email.
And maybe the weirdest too? What's going on here?
Weather experts say a warming planet has led to changed atmospheric circulation patterns in the jet stream, the fast-moving river of air that separates cold air from warm air and dictates weather patterns across the globe. They say the features within the jet stream that bring clouds and precipitation or dryness and extreme temperatures — low-pressure troughs and high-pressure ridges — are changing their movement and duration, creating unusual weather patterns that lock in place and cause major floods, cold spells and heat waves.
Consider McGrath, Alaska.
The town in May set 10 temperature records — six for daily lows around the middle of the month and four for daily highs near the end of the month, reported Anchorage television station KTVA.
Then, on June 17, McGrath hit an all-time record of 94 degrees.
Now consider Chicago.