This region usually experiences:

• Dry, warm to hot summers
• Wet, mild to cool winters. 
• Rainfall is expected in March to May as the ‘autumn break’. 
• Frequent winter rainfalls replenish soil moisture and maintain vegetation and stream flows through the dry summers.
• Summer average maximum temperatures: 22-24°C near the coast and ranges, 25-27°C in the urban area and inland. 
• Winter average maximum temperatures: 12-14°C but higher in urban areas.
• Frosts occur inland but rare in coastal and urban areas.
• Annual rainfall ranges from less than 600mm in the region’s west to more than 1,400mm in the Dandenong Ranges. 

However, this climate is changing. The average annual air temperature across this region has increased by 0.8°C to 1.0°C over the last century and more rapidly since 1960. 

High-confidence predictions show further temperature rises of similar magnitude by 2030. By 2050, cold years could be warmer than most of the region's current climate’s warm years.

A general fall in mean annual rainfall has been observed since the mid-1970s. Rainfall losses have been most pronounced in Autumn-Winter.  Predictions for rainfall losses are less certain but general and progressive losses in winter-spring rainfall are expected to continue.

Soil moisture and catchment runoff are confidently predicted to decline; driven largely by changes to rainfall and evapotranspiration.

Climate change is likely to affect all parts of living systems in this region and to multiply and complicate existing pressures. It challenges assumptions that natural resource management might be able to preserve present or restore past conditions. 

More information about potential climate change effects is available on the  Port Phillip & Westernport Regional Catchment Strategy,