Know any diabetics, dialysis patients or pacemaker wearers? Is your water pressure derived from pumps or gravity? Was your automobile built since the mid-seventies? How about the trucks that deliver groceries to your local market?
An awful lot of really important stuff is going to quit working in this event. Think of your worst day as a geek, and multiply by ninety days. Be prepared to take care of yourself, your family, and your neighbors because the folks reading this will be rebuilding the stuff that falls apart.