In my reply to Mage's comment about spring I forgot to mention St. Patrick's Day in Chicago. While it's true that Chicago mostly went directly from winter to summer the exception was St. Patrick's Day. It could snow on March 16 and/or March 18, but March 17 was always beautiful. I was certain Mayor Daley (Richard J., not the current one) had an in with the god of weather. The parade always marched under blue skies. Now that they've moved the celebrations to the weekend before, I don't know what happened in Chicago. It was a cold, rainy day here. Today is beautiful.
You can see a great photo of the 'green' Chicago River here.