Hi, i guess you have to change some code in the *.js file of mmm-openmapweather.
there is a row with //,“50n”: “wi-night-alt-cloudy-windy”
due to the point that there is no image for the “fog at night” i used the regular fog image.
now it works for me , yes it is not 100% correct, but better than nothing.
iconImageTable: {
"01d": "sunny.png",
"02d": "partlysunny.png",
"03d": "partlycloudy.png",
"04d": "cloudy.png",
"09d": "sleet.png",
"10d": "rain.png",
"11d": "tstorms.png",
"13d": "snow.png",
"50d": "fog.png",
"01n": "nt_clear.png",
"02n": "nt_cloudy.png",
"03n": "nt_mostlycloudy.png",
"04n": "cloudy.png",
"09n": "nt_sleet.png",
"10n": "nt_rain.png",
"11n": "nt_tstorms.png",
"13n": "nt_snow.png"
,"50n": "fog.png"