This study investigates the three-dimensional fire weather conditions associated with a foehn event in the South Island of New Zealand. The Weather Research and Forecasting (WRF) numerical weather prediction model is used to simulate the synoptic and mesoscale weather processes associated with the foehn event. The fire weather conditions are assessed using weather variables and two fire weather indices; the New Zealand Fire Weather Index and Continuous Haines Index. The foehn winds, known locally as the Canterbury Northwester, affect the central eastern South Island and are formed due to an interaction between the synoptic northwesterly flow and the Southern Alps mountain range. The atmospheric stability is assessed upwind of the Southern Alps and related to orographic blocking of the low-level synoptic northwesterly winds. The thermal effect of the foehn resulted in elevated air temperatures and lowered relative humidities across the central eastern South Island. Mountain lee waves were generated over the eastern South Island and their impact on fire weather conditions is assessed. The results demonstrated that the foehn winds and mountain lee waves can significantly affect fire weather conditions, both near the surface and aloft, in the central South Island of New Zealand.