The waiting is the hardest part as lava from Hawaii's Kilauea volcano creeps slowly through the community of Pahoa, where residents never know from hour to hour whether they should pack up and leave, even as they can hear the crackle and hiss of gases exploding from the 2,000-degree river of molten rock.
Lava has a mind of its own, Hawaii County Civil Defense Director Darryl Oliveira said Tuesday. It can change direction as the flow widens on either side and snake off in new rivulets that experts call "fingers." That means that even though the lava flow is generally heading in one direction, structures off to the side can come into harm's way.
"These are very difficult to forecast," Oliveira told NBC News. "We're watching it very closely today."