Here’s a chilling sign that low unemployment has its downsides: Maine can’t find enough snowplow drivers.

The state Department of Transportation has about 50 openings among about 700 positions and expects 30 snow storms in the season that stretches from mid-November to mid-April. Exacerbating the problem: some cities like Portland hire their own drivers and pay more, and private sector demand for experienced drivers is also high.

“It’s...