Which is a common climate characteristic of the Northeast? extreme humidity
ongoing tornadoes
frequent winter storms
extraordinary precipitation

C, frequent winter storms.

Explanation:

In the northeast, it usually does not experience tornadoes, it has low humidity and an average amount of rainfall. But the northeast has a lot of winter storms.

D. Extraordinary precipitation OR

C. Frequent winter storms

Explanation:

The northeast is near the ocean. Precipitation is most likely to be extremely high.

Extreme humidity is down towards the south.

Ongoing tornadoes is in the middle of the U.S. or in the midwest (Tornado Alley).

Frequent winter storms happen in mostly the northern states and in the northeast, but the key word is precipitation.

I could be wrong. It could be C, and D could apply to the western coast, but that's how I reason through it.