The Obama administration is planning a series of actions this summer to rein in greenhouse-gas emissions from wide swaths of the economy, including trucks, airplanes and power plants, kicking into high gear an ambitious climate agenda that the president sees as key to his legacy.

The Environmental Protection Agency is expected to announce as soon as Wednesday plans to regulate carbon emissions from airlines, and soon after that, draft rules to cut carbon emissions from big trucks, according to people familiar with the proposals....