Fog Cloud
You create a 20-foot-radius Sphere of fog centered on a point within range. The Sphere is Heavily Obscured. It lasts for the duration or until a strong wind (such as one created by Gust of Wind) disperses it.
Using a Higher-Level Spell Slot. The fog's radius increases by 20 feet for each spell slot level above 1.
Fog Cloud 5e 2024 vs. 2014 edition differences
The 2014 version states the fog disperses with moderate or greater wind (at least 10 mph), while the 2024 version specifies dispersal by a strong wind, such as from Gust of Wind. The 2014 version explicitly mentions the radius increasing by 20 feet per slot level above 1st; the 2024 version states the radius increases by 20 feet per slot level above 1 without specifying the method.