Seattleites brave the snow during the 2012 winter season.

If you thought the over-hyped storm this October meant that autumn and winter will be mild — think again. Experts warn La Nina is coming. And that means some significant weather hazards.

“Get ready for these kinds of things, whether it’s wind, flooding or snow,” said Ted Buehner with the National Weather Service. “It’s that time of year.”

October already has exceeded average rainfall

Buehner said the coming seasons will hold “active, hazardous weather.” That means snow, rain, wind, flooding, and landslides. The Northwest is about to experience a La Nina — following the El Nino pattern last autumn and winter. More specifically, it is predicted to be a weak / neutral La Nina, and that particular type has brought severe weather to the region in the past.

“Historically, it tends to give us some pretty active fall and winter seasons,” Buehner said. “I’d say we’ve already seen a bit of that.”

For example, this October far exceeded average rainfall for the month within two weeks. Buehner points to other weak / neutral La Nina’s to make the point. The Snomegedon of 2008 is one such season. The winter of 1997 was another season. Back then, the Puget Sound region had as much as 2 feet of snow dumped on it at once.

The follow-up to the heavy snow is important, too. In both historic cases, heavy rain followed in January causing severe flooding and landslides.

And in case you forgot what La Nina is:

“La Nina is when the sea surface temperatures in the eastern Pacific tropical waters – west of Peru – are cooler than average,” Buehner said. “As a result, we tend to have the Pacific storm track and the jet stream spending a lot more time at our latitude, versus El Nino which is what we had last winter when the waters are warmer than average. As a result, the jet stream spends a lot more time across California.”