Wildfire Disaster Funding Act of 2013 - Amends the Balanced Budget and Emergency Deficit Control Act of 1985 (Gramm-Rudman-Hollings Act), with regard to sequestration adjustments, to require any adjustments in enacted appropriations for wildfire suppression operations in the Wildland Fire Management accounts at the Department of Agriculture (USDA) or the Department of the Interior for a fiscal year, to be the amount of additional new budget authority provided for wildfire suppression operations in the appropriations Act, but not to exceed $2.689 billion in such authority in each of FY2014-FY2021.

Defines "additional new budget authority" as the amount specified in an appropriations Act for a fiscal year to pay for wildfire suppression operations, but only to the extent such authority exceeds 70% of the average costs for wildfire suppression operations over the previous 10 years.

Prescribes requirements for any request by the Secretary of the Interior or the Secretary of Agriculture for supplemental appropriations necessary for wildfire suppression operations.