How Fast Is Speed of Sound (air)?

Sound travels at 343 m/s in air at 20°C — that's 1,235 km/h. It's why lightning appears before thunder: light reaches you almost instantly while sound takes about 3 seconds per kilometre. Sound travels 4× faster in water and 15× faster in steel.

The speed of sound varies with temperature: it's about 1,235 km/h at 20°C but rises by about 0.6 m/s for every 1°C of warmth.

• Sound travels 4× faster in water
• Light is 880,000× faster