Original: 110-120 degrees fahrenheit) and wind speeds in excess of 100 km/h, precipitated by an intense heat wave, fanned the fires over large distances and areas, creating several large firestorms and pyrocumulus systems, particularly north-east of Melbourne, where a single firestorm accounted for 120 of the 173 deaths.
Simplified: The wind blew the fires over large distances and areas, creating several large firestorms.