Despite a year of near-level rain and snow across California, the number of dead and dying trees continues to skyrocket into the tens of millions.The U.S. Forest Service released new numbers for 2016 and estimates 66 million dead trees are present in the most fire-prone areas of the state.In October 2015, the tree-mortality estimate was 40 million."I've never seen anything like it," said Jeff Moore, an aerial surveyor with the U.S. Forest Service. "There are so many more new dead trees out there on the landscape."Moore went on surveys in May, covering a six-county region along the central Sierra Nevada including Kern, Fresno and Tuolumne counties."It's just two guys looking out the window of an airplane doing their level best to record what they see," Moore said.The U.S. Forest Service estimates there are nearly 4 billion trees statewide. Moore said the number represents an overpopulation of trees that has grown due to wildfire prevention over the decades."The forest in many areas of the state are so overcrowded already because we have been keeping fire out of these areas," Moore said. "When a drought like this happens, it's really going to have a drastic effect on those trees because there just isn't enough water to go around."The tree mortality progression due to drought and bark beetles has escalated exponentially since 2010:- From 2010 to 2014, 14 million dead trees were reported- In 2015, an additional 26 million dead trees were reported- Preliminary 2016 numbers also report an additional 26 million dead treesThe years combined total is 66 million trees -- and the number expected to grow.Tuolumne County is one of the hardest hit areas. Crews are already starting to remove thousands of dead and dying trees."We have had to really triage this situation and we are really focusing on the trees that are near evacuation routes, near people's homes and critical infrastructure," said Daniel Berlant, spokesman for Cal Fire. "That fire is going to burn so fast and do so much destruction."Although the beginning of the year reached near-average levels of precipitation, the foliage has now become a healthy batch of ground fuel as conditions dry.Berlant said the most impacted areas have now spread to Placer, El Dorado, Amador and Calaveras counties. The 10-county region along the Sierra Nevada is eligible for state funding.The U.S. Forest Service will conduct additional aerial surveys throughout the state in the summer and fall."As the U.S. Forest Service continues to do aerial surveys through the rest of the state, that number will continue to increase dramatically," Berlant said.This dangerous number translates into the possibility for a more destructive wildfire season.