So, Diwali is finally over, well before you could realize that it ever came ! You were busy watching the Arsenal play over the last weekend and had no idea that Diwali was approaching until your FB wall was flooded with the greetings. And by the time you had an idea your office work left you with absolutely no time to prepare for it. It happens. Sadly, you are not in India, you may say. Its so difficult to notice it here. But I would say, gladly, you are not in India. Cheer up, Diwali is not gone yet. Here are 3 of your options.
1. The Hindu Temple of Greater Chicago
10915, Lemont Road, Lemont, IL
Diwali Cultural programs begin at 2 pm and will be followed by grand Fireworks 7 pm onwards on Saturday, the 17th. Check htgc.org for more.

2. Sri Venkateswara Swami Balaji Temple
1145 W, Sullivan Road, Aurora, IL
Diwali Pooja begins at 4 pm and ends with Fireworks at 7:30 on Saturday, 17th November. Check out balaji.org for more.
3. Shri Swaminarayan Temple
397, Northgate Parkway, Wheeling, IL
Their 5 day celebrations get over on Sunday, 18th November with Bhajan, Kirtan and Katha in truly traditional Gujarati style. Be there by 10 AM. Check swaminarayan.ws for more.
I am sure if you search for them you will find some more. I hope with these options you wont regret missing the actual Diwali on 13th. Happy Diwali, once again !
Harsh Vardhan