u/MalvmMalvm

I thought you needed a cold or warm front to get a thunderstorm, but it seems like you just need a strong updraft and wet air. The sun has been doing a great job of heating up the ground all day and in the evening, the ground heats up the cooler air. The now warm air near the ground is more buoyant than the air around it so the air rises rapidly, taking our characteristic humidity with it. This warm, wet air contacts colder air higher up, the humidity condenses into water drops, which eventually get big enough to fall. Once the air cools down the updraft dies and the thunderstorm dissipates. That's why our storms didn't last long; the updraft got broken up my the storm itself.

TL;DR: The sun heats the ground, which heats the air, which rises and causes a storm that cools down the ground and the air killing the storm. Our updrafts were wimps compared to the cooling of the storm so the storm didn't last long.

Source: https://www.nssl.noaa.gov/education/svrwx101/thunderstorms/