This is example of how to fetch Openweathermap API to show current and forecast weather in some cities on the Leaflet map and combine it with weather map layers. It's based on Kosmosnimki prototype app to get city local time shift in forecast query. You can add more cities or choose different ones.
var owm = new L.OWMLayer(options); map.addLayer(owm);
L.OWMLayer constructor are available: