You wouldn’t know it to look outside, but spring has arrived. All the usual signs of spring are being blanketed as we speak, but there’s one sign even another snowfall can’t cover up. Hole in the Wall Custard, Oak Park’s longstanding south side ice cream tradition opened yesterday. The storefront is so small (hence the name) that it’s address is 901 1/2 S. Oak Park Ave., just south of the Eisenhower Expressway. It’s easy to miss right now, but once the temperatures rise (no, really) you’ll see the line snaking out the door. We may be in for another White Easter, but don’t despair. Global warming is on the way.