I’m not seeing much lag either on my computer. But keep in mind that geolocation can be slow, especially on mobile when the GPS is having trouble finding you (5-10 seconds is not unusual). Maybe you can display a message like “Getting weather information” while waiting for the data to come back so that the user knows what is going on.
Concerning icons, the FreeCodeCamp weather API doesn’t always provide an icon with its data, I don’t know why. I made my app more general so that the user can get weather from anywhere in the world as an alternative to geolocation (it’s much faster, even on broadband) so I’ve tested getting weather for all sorts of places, and sometimes you get an icon, sometimes you don’t. Haze and snow seem to be particularly prone to missing the icon. There was an interesting thread not long ago that mentioned getting weather icons independently from the API.