How hot is a fireball?
The air around a fireball heats to several thousand degrees, forming glowing plasma, but the meteoroid itself only melts at its surface for a few seconds.
A fireball is bright because the air around the meteoroid becomes extremely hot.
The air. As a meteoroid ploughs through the atmosphere at tens of kilometres per second, it compresses the air in front of it. This creates a shock layer where air reaches temperatures of several thousand degrees Celsius, often quoted at around 4,000 to 5,000 °C or more for bright fireballs. At such temperatures, air molecules break apart and become ionised plasma, glowing brightly. Spectra show emission from both air and vaporised meteoroid material.
The meteoroid's surface. The surface of the meteoroid melts, at roughly 1,500 to 2,000 °C for stony material, and the melt is constantly blown away. This process, called ablation, carries heat away with it, so the meteoroid itself does not get hot throughout.
The interior. Because rock conducts heat poorly and the bright flight lasts only seconds, heat penetrates only a millimetre or so. The interior keeps the temperature it had in space, which may be well below freezing. This is why meteorites are generally not hot when they land.
After the glow. Once the meteoroid slows below a few kilometres per second, usually 15 to 30 kilometres up, heating stops. The remaining fall through cold upper air, called dark flight, lasts minutes, and the thin melted surface solidifies into fusion crust.
The glowing trail of hot gas can persist for seconds or minutes as a persistent train, cooling and slowly dispersing.