Latest indications are that we will soon be entering into another El Nino event, so now is a good time to re-examine the effects that El Nino can have in New England and in the United States as a whole.
First, a quick refresher course on what an El Nino is. An El Nino event always begins with a warming of the waters in the eastern equatorial (near the equator) Pacific Ocean. Using satellites and ocean buoys, NOAA scientists constantly monitor the temperature of all ocean waters, and it has been determined that when the eastern equatorial Pacific Ocean gets warmer than average, global weather patterns change, causing abnormal weather conditions to be seen across parts of all seven continents. This "warming" of the Pacific Ocean occurs roughly once every 3 to 7 years, and the amount of ocean warming is proportional to the severity of the El Nino. In other words, if the eastern equatorial Pacific ocean gets to be 2 or 3 degrees Celsius above normal, that is classified as a strong El Nino, and the worldwide weather effects will be much greater compared to a weak El Nino, when the eastern equatorial Pacific ocean is only 0.5 to 1.0 degrees warmer than normal. Again, this can easily be quantified by measuring the sea surface temperature of the eastern equatorial Pacific Ocean. For example, the years 1997-98 saw one of the strongest "El Nino's" on record, and during that Winter, several northern states from Wisconsin westward, saw one of the warmest winters in their recorded history, while much of the southern half of the country saw a very cool and stormy winter season. And the Atlantic Hurricane season of 1997 was very quiet, with only 9 named storms, not to mention zero tropical storms in August, which is typically one of the most active months. Conversely, sometimes an El Nino can be so weak that its effects are barely felt for most of the globe.
In a nutshell, an El Nino event disrupts the jet stream as well as global ocean currents, which in turn brings about abnormal weather conditions. This can have a detrimental effect on many industries worldwide, especially farming and fishing.
As for Southern New England, El Nino doesn't really have much of an effect on our weather patterns, however there are some data that show a warmer-than-normal period that begins about 4 months after the beginning of the El Nino event. So if this El Nino begins before Summer arrives, history has shown that there will be a tendency for SNE to have a warmer than normal Autumn season. Otherwise, the effects of an El Nino tend to affect other parts of the U.S. much moreso than here in SNE.
Regarding Hurricane Season (June 1st - December 1st), history has shown that fewer tropical systems will form in the Atlantic Ocean in an El Nino year, compared to a non-El Nino year. So from Maine to Florida, residents actually benefit from an El Nino event.