McArthur's fire-danger meters expressed as equations

McArthur's fire-danger meters for grasslands (Mark 3) and forests (Mark 5) have been widely used in Australia for fire-danger forecasting and as a guide to fire behaviour. We present a set of equations to describe the data provided on these meters plus equations pertinent to the recently-produced Mark 5 grassland meter. The equations provide a simple method of describing the forecasting system and are particularly useful for machine processing, and modeling.