One of the nation’s most important climate fights is currently playing out under the radar in California, where state residents are weathering an unprecedented tropical storm. Oil and industry lobbying groups are spending millions in a last-ditch attempt to block first-of-its-kind legislation that would require thousands of large companies doing business in the state to fully disclose their carbon emissions, a move that would effectively set national policy.

In the final weeks of California’s legislative session, which ends in mid-September, State Assembly members are expected to vote on the climate transparency bill. With a federal version of the measure still delayed — and nearly certain to face lengthy legal challenges from industry — California’s legislation could expedite a public reckoning over corporations’ true contributions to climate change.

The bill has already passed the State Senate, and if it survives a secretive appropriations hearing later this month, it will go before the full Assembly — where a previous version failed by just four votes last year following a fierce opposition campaign.