CHEYENNE, Wyo. (AP) — Drought conditions have posed a challenge but have not stopped Wyoming’s ambitious cloud-seeding research project.

The state has invested about $13 million since 2005 in the project, which seeks to determine whether dispersing certain substances in the atmosphere can increase snowfall and the amount of snowpack in several of the state’s mountain ranges. Officials say it’s the most comprehensive research-based project undertaken to determine whether cloud seeding works.