LAHTI, Finland — Tuesday at Lahti’s venue for the 2017 Nordic World Ski Championships, the sun sets early. Although technically sunset was 5:22 p.m., the sun on this clear-sky day was still wintertime reluctant. It seemed too short a time for the sun’s transect to thaw Lahti. Temps were in the mid-to-low 20 degrees Fahrenheit. But a brisk wind called for down coats and insulated pants for those not actively skiing — in the shade, it...