A La Niña winter coming in Iowa: What does that mean?

Sure, we’re still only in September and deep in the throes of some near 90-degree temperatures, but the winter season is coming, and with it a familiar weather pattern: La Niña. What even is La Niña?La Niña and El Niño are the two phases of the El Niño Southern Oscillation (ENSO) climate pattern, which originates down along the Equator in the eastern Pacific Ocean. During La Niña, the trade winds blowing from the east get stronger than normal. This pushes warm surface water into the western Pacific and allows cold water from the deep ocean off South America to rise up in its place. This movement of heat affects weather worldwide. Off the west coast of North America, La Niña pushes the jet stream northward, altering how that belt of strong winds blows across the US. La Niña and IowaSince La Niña results in the jet stream flowing northwest to southeast across America, the northern tier of the country often ends up colder than normal. Iowa, being closer to the jet stream’s path, can be colder overall, but with frequent swings in temperature. La Niña winters in our state often bring frequent fast-moving storm systems that ride the jet stream down out of Canada. Unlike big winter storms that travel up from the south and grab lots of moisture from the Gulf of Mexico, these Canadian systems are generally drier and can’t produce more than a few fluffy inches of snow & some gusty winds. On the other hand…one of these systems blanketed central Iowa with 12″+ this past January.Other factors matter as wellAll La Niñas aren’t equal, however. Sometimes the eastern Pacific is just slightly colder than normal. Other times it’s much colder than normal.La Niña is also just one of many climate patterns that affect us. Sometimes these patterns conflict with each other. For example, the last five La Niña winters in Des Moines have shown no clear trends in snowfall or temperature. Either way, the trends point toward this La Niña ending by next spring.

Sure, we’re still only in September and deep in the throes of some near 90-degree temperatures, but the winter season is coming, and with it a familiar weather pattern: La Niña.

What even is La Niña?

La Niña and El Niño are the two phases of the El Niño Southern Oscillation (ENSO) climate pattern, which originates down along the Equator in the eastern Pacific Ocean.

During La Niña, the trade winds blowing from the east get stronger than normal. This pushes warm surface water into the western Pacific and allows cold water from the deep ocean off South America to rise up in its place.

This movement of heat affects weather worldwide.

Off the west coast of North America, La Niña pushes the jet stream northward, altering how that belt of strong winds blows across the US.

La Nina and Iowa

Since La Niña results in the jet stream flowing northwest to southeast across America, the northern tier of the country often ends up colder than normal.

typical la niña winter

Iowa, being closer to the jet stream’s path, can be colder overall, but with frequent swings in temperature.

La Niña winters in our state often bring frequent fast-moving storm systems that ride the jet stream down out of Canada.

Unlike big winter storms that travel up from the south and grab lots of moisture from the Gulf of Mexico, these Canadian systems are generally drier and can’t produce more than a few fluffy inches of snow & some gusty winds.

On the other hand…one of these systems blanketed central Iowa with 12″+ this past January.

Other factors matter as well

All La Niñas aren’t equal, however. Sometimes the eastern Pacific is just slightly colder than normal. Other times it’s much colder than normal.

recent moderate la niñas

La Niña is also just one of many climate patterns that affect us. Sometimes these patterns conflict with each other. For example, the last five La Niña winters in Des Moines have shown no clear trends in snowfall or temperature.

Either way, the trends point toward this La Niña ending by next spring.

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