A frost is defined as the occurrence of an air temperature of 0°C or lower, measured at a height of between 1.25 and 2.0 m above soil level, inside an appropriate weather shelter such as a Stevenson screen.
Frost occurrence was calculated as days per annum having a daily minimum temperature (Tmin) < 0°C (frost), < -1°C (severe frost), and < -2°C (very severe frost), for the historical and intermediate future periods, as well as the change.
The highest risk of frost to deciduous fruit production is in the late winter and spring months (July to November). The frost occurrence for each of these months was calculated using the same Tmin thresholds, for the present and intermediate future periods.