An Xcel Energy substation at 14th and Jackson streets in east Denver burst into flames yesterday, sending a long plume of black smoke into the air (via the Denver Daily News [2]). The explosion left an estimated 37,000 people without power, including many at Rose Medical Center, which experienced evacuations. Power was expected to be restored to the outage area---from Quebec to Humboldt streets between First and 24th avenues---sometime this morning, reports The Denver Post [3], which points out that the incident left traffic lights inoperative, stranded dozens in elevators, and lured gawkers into the streets. The explosion came at 6:30 p.m., when people likely had their air conditioners cranked on what was the hottest day of the year so far. The high temperature yesterday was 94 degrees [4], about 15 degrees higher than average for this time of year. Xcel investigators have not yet identified the cause of the explosion.