Method
Frost
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.
Maps
Map Information
In July and August, the present frost risk (Tmin < 0°C) is highest, with many inland areas experiencing more than 4 frost days per month. Into the intermediate future of the 2050s, this level of risk is reduced to the interior and high-lying areas. Other areas in the interior and along the coast essentially become frost-free or experience less than 1 frost day during these months. The present frost risk is reduced in September but still widespread, including some coastal areas, while in October and November it is mostly limited to the interior and high-lying areas. The maps for the projected intermediate future indicate strong shrinkage in the high risk areas, and the November of the future could become almost entirely frost-free.
The present patterns for severe frost (Tmin < -1°C) and very severe frosts (Tmin < -2°C) show a similar higher risk in July and August compared to later months, but spatially shrunk compared to frost. Into the intermediate future, some risk of severe and very severe frost remains in small areas from July until September, but in October and November the risk becomes negligibly small everywhere.