El Nino is a climate pattern of unusual warming of the ocean water in the Eastern Tropical Pacific, caused by a weakening of east winds in this region. El Nino affects global weather patterns, and usually leaves Montana with a mild and dry winter.
This strong El Nino was anything but "normal" up until recently when heavy rain and mountain snow hit the southwestern United States, and severe storms hit the Gulf Coast. The Great Lakes have been typically warm and dry, the northeast has gotten more snow. The Pacific Northwest and Northern Rockies have been dry.
This El Nino is now coming to an end as the tropical water in the Eastern Pacific is cooling. Forecasts now suggest a La Nina will develop by this summer. Historically, a strong La Nina has followed strong El Nino events in the past.
Montana's snowpack continues to be below normal, creating concern for this upcoming wildfire season.
Following the historic 1997-98 El Nino event, a La Nina developed by the summer of 1998. That summer in Montana started off with very wet and cool conditions for the month of June, with average temps and slightly above average precipitation in July, and above average temperatures and near average precipitation in August. That wildfire season was below average for Montana and the entire west.
No two El Ninos are exactly alike, and neither is weather patterns that follow. But looking back at what has happened in the past makes looking ahead to this summer and winter a little more hopeful.