Austin Nichols is worried. Since landing the role of Spencer Monroe, a sharp-shooting lookout on AMC’s The Walking Dead, he is usually concerned about zombies. Not today. Here, on an early March afternoon in Austin, Texas, it’s all about rain. A massive El Nino-generated low pressure system has hunkered down over the Lone Star State and now Nichols’s afternoon plans – a motorcycle ride to Opie’s BBQ – are in jeopardy.