There are 3 ingredients needed for a thunderstorm: 1. moisture (water vapor) in the air near the surface 2. instability - relatively large decrease of air temperature with height 3. read more
Thunderstorms can occur at any time of day or night, but they're most common in the afternoon because that's when the temperature near the surface is generally at its highest under conditions of sunny skies. That warming near the surface means the air is likely to be the most unstable during the day. read more
Most thunderstorms occur in the late afternoon or evening after maximum radiational warming. In the late afternoon, instability tends to be highest due to daytime heating increasing the temperature gradient between the PBL and the middle levels of the atmosphere. read more