Melbourne sits on the shore of Port Phillip Bay in southern Victoria, at approximately 37.81°S, 144.96°E. It has a temperate oceanic climate (Köppen Cfb) with warm summers and cool, damp winters, but it is above all famous for its changeability: sitting on the boundary between the hot interior and the cold Southern Ocean, it is renowned for experiencing 'four seasons in one day'. Being in the Southern Hemisphere, its seasons are reversed relative to the Northern.

Summer, from December to February, is pleasantly warm on average, with highs usually around 25–26°C and cool nights. It is the driest season, but far from stable — when northerly winds draw air from the desert, fierce heatwaves can send temperatures past 40°C, as in the run of mid-40s days during the 2009 and 2014 heatwaves, with the record 46.4°C set in February 2009. These hot spells are typically broken abruptly by a 'cool change' behind a southerly front.

Winter, from June to August, is cool, cloudy and often windy rather than severely cold. July, the coldest month, averages daytime highs around 14°C and nights near 6°C, and outbreaks of Antarctic air can push nights close to 0°C. Genuinely freezing days are rare and snow in the city almost unheard of, though the surrounding hills and ranges see it regularly.

Melbourne is drier than Sydney or Brisbane, receiving around 600 mm a year in the city centre, spread fairly evenly with a slight late-spring peak around October and a relative winter minimum in quantity. Rather than long soaking rains, it tends to get fleeting, sometimes heavy showers that blow through in minutes before the sun returns — part of the 'four seasons in one day' effect. Rainfall varies sharply across the metro area thanks to the rain shadow of the Otway Ranges. Live rainfall, humidity, and pressure readings for the city are shown in the panels above.

The city's hallmark is rapid change: strong cold fronts sweeping off the Southern Ocean can drop the temperature ten degrees in an hour, bringing squalls, hail and sudden downpours, especially in spring and summer. Shallow, enclosed Port Phillip Bay also creates a local 'bay effect' that can intensify showers over the southeastern suburbs while the rest of the city stays dry.

To follow any single measurement in Melbourne more closely, use our live instruments: the online barometer for atmospheric pressure, the thermometer for temperature, the hygrometer for humidity, the anemometer for wind speed, the wind vane for wind direction, and the rain gauge for rainfall.