When the temperature is significantly warmer in the northern part of North America, a/an oscillation is taking place.

When the temperature is significantly warmer in the northern part of North America, a Southern Oscillation is taking place.

Explanation:

One very curious but very influential occurrences when it comes to weather conditions is the Southern Oscillation. It is not something that happens regularly, but instead, it can happen on two years distance, 5-year distance, or anything in between. What happens basically is an intense warming up of a huge area of the eastern part of the Pacific Ocean.

The warming up of a large part of the largest ocean in the world influences the weather conditions all over the planet, though in some regions like the ones that are around the Pacific it has a big influence, in the regions that are further away it has much smaller influence. Some areas get long and hot droughts, some places experience heavy rainfall for a long period of time, while some places, like the northern part of North America, experiences unusually high temperatures for its latitude.