I'm trying to access openweathermap api forecast, in somepoint I need to take decision based on the climatic layers so kindly help me to convert as WFS Layer(Geoserver) from the api. Thanks. I'm JS Beginner know Leaflet and Geoserver
You don't say much about what the API in question returns. If it is a WFS itself then you can cascade it through your GeoServer instance, which will allow you to serve it out as a WFS and a WMS.
If it returns some other format, you can write a custom datastore by following the steps in this tutorial. When you have a working jar package you can drop it into the WEB-INF/lib folder and restart GeoServer and it should appear as a new datastore.