SIOUX FALLS, S.D. (KELO) — As we enter the fall, thoughts start to go to what kind of winter we may have. One of the driving forces behind the winter forecast is that it will be another La Nina year.

La Nina occurs when the sea surface temperatures along the equator in the Pacific Ocean are cooler than average. The cooler than average trend has an impact on the jet stream and gives certain patterns around the globe.

For us in the United States, it includes cooler than normal temperatures in the Pacific Northwest to the upper plains. Which is a little ironic considering the above-average temperatures through most of the summer in the Pacific Northwest.

With the cooler air, it tends to be wetter than average in the northwest United States as well as the corn belt. The southern US tends to be drier.

But, not all La Ninas are the same. They vary in their strength from year to year or whenever they show up.

Of course, La Nina will not be the only thing I look at as I start to piece together a winter forecast. That winter forecast will come out in November during the KELOLAND Live Doppler Winter Special.