On this edition of Your Call’s One Planer Series, we're discussing a new UC Berkeley study that finds the heat index calculated by National Weather Service meteorologists may underestimate the perceived temperature on the most sweltering days, sometimes by more than 20˚F. Last week, a blistering heat wave smashed records in at least a dozen California cities. What is the heat index and why is it important? Guest: Dr. David Romps, professor in the Earth & Planetary Sciences department at University of California Berkeley