Coal production during in the first quarter of 2016 was the lowest its been since 1981. According to the US Energy Information Administration, coal production in the Power River Basin dropped nearly 30% from the fourth quarter of 2015. That is a bigger drop than in any other region.

Demand for coal is down because of low natural gas prices, competition from renewables, and environmental regulations. An unusually warm winter also reduced demand, so companies cut production.

But those companies are hoping that unseasonably warm temperatures will carry over into summer, boosting demand for air conditioning, and with it, electricity. But the current long-range forecast is for a slightly cooler than average summer in most of the country, which could continue to put pressure on the coal industry.