Almost 250 different fires started in Yellowstone and the surrounding National Forests between June and August. Seven of them were responsible for 95% of the total burned area. At the end of July, the National Park Service and other agencies had fully mobilized available personnel, and yet the fires continued to expand. Smaller fires burned into each other, propelled by dry storms which brought howling winds and dry lightning strikes but no rain. On August 20, the single worst day of the fires and later dubbed "Black Saturday", more than were consumed during one of many intense fires. Ash from the fires throughout the park drifted as far away as Billings, Montana, to the northeast. The wind driven flames jumped roads and firelines, and burning embers started new fires a mile (1.6 km) or more ahead of the main fires. Ground fires raced the fuel ladder to the forest canopy and became crown fires with flames over high. On that single day, more Yellowstone land burned than in all other fires combined since the establishment of the park. Throughout the summer, fires made huge advances of a day, and there were even occasions when more than in one hour were recorded.