Wildfires and Hurricanes Indemnity Program Extension Act of 2018 This bill amends the Bipartisan Budget Act of 2018 to extend the Department of Agriculture 2017 Wildfires and Hurricanes Indemnity Program. (Under current law, the program provides disaster payments to agricultural producers who suffered crop, tree, bush, and vine losses resulting from hurricanes and wildfires that occurred in the 2017 calendar year.) The bill extends the availability of the funding for the program through December 31, 2020, and expands the program to include losses resulting from hurricanes and wildfires occurring in calendar year 2018.