The Pacific Northwest is currently experiencing the worst heat wave in its history. All-time records were set in Portland, Seattle and Lytton in B.C., which also just broke the Canadian record for the hottest temperature at 116 degrees. CBS News reports that this heat wave is "of an intensity not recorded by modern humans" and, by one measure, it's "more rare than a once-in-a thousand year event." Jeff Berardelli, a meteorologist, explains why this heat dome is occurring and why it will "become more frequent, more extreme and deadly in the future."
