By John Dodge

CHICAGO (CBS) — As Chicagoland finally puts the cold, miserable winter behind, the outlook for summer appears to be a season of cooler temperatures with an average amount of rain.

According to the National Weather Service, the region has an “enhanced chance” for below normal temperatures from June through August

An El Nino episode is developing in the tropical Pacific, and this tends to favor cooler conditions in the summer here.

Timing is the key: If El Nino conditions set up soon, then cooler temperatures are possible.

However, if it arrives later there is an equal chance of warmer than average temperatures as well.

El Nino develops when Pacific Ocean temperatures rise higher than normal, changing weather patterns across the United States.

In other El Nino summers over the past 30 years, 60 percent were cooler than normal, while 27 percent were warmer.

Average high temperatures for June though August are in the mid to low 80s, with lows in the mid to low 60s.

Typically there are about two weeks worth of days above 90 in the summer.

During the past two El Nino seasons (2004, 2009) there have been four each year.

Between December and March, Chicago experienced its coldest period on record, where have been kept since 1872.

The official “meteorological winter”–from December through February–was the third coldest on record.

The reason it was so cold? A change in the upper atmosphere caused the typical cold air in Canada to plunge farther south, hitting Chicago hard.

Combining with the cold, it was also the third snowiest season ever.