(CNN) If you feel like the weather has been out of control in much of the United States, you're right. A weather pattern that stuck around longer than usual created a dangerous mix of conditions.

It's not a coincidence. CNN meteorologists say it's all tied to a jet stream pattern.

Jet streams are rivers of fast-moving air up in the atmosphere -- around the altitude where planes normally fly -- that push air masses, typically from west to east but not in a straight line. They are key to determining the weather as they separate cold air from warm air.

The jet stream pattern over the United States has been stuck for days, leaving cooler and wetter conditions in the West, and hotter and drier conditions in the East, CNN meteorologist Brandon Miller said.

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