Map from Google - Melbourne

In Melbourne, a city of southern Australia and capital of the state of Victoria, the climate is subtropical oceanic, with mild winters and pleasantly warm summers.
Here are the average temperatures.
Average temperatures - Melbourne
MelbourneJanFebMarAprMayJunJulAugSepOctNovDec
MelbourneJFMAMJJASOND
Min (°C)141413118766891112
Max (°C)262624201714131517192224
Min (°F)575755524645434346485254
Max (°F)797975686357555963667275

The weather is often variable, in fact the city is located enough to the south to be affected by the flow of westerly winds, which bring low pressure systems for several months a year.
Rainfall is not very abundant, since it amounts to 650 millimetres (25.5 inches), but it is well distributed over the seasons, so that there is no real dry season. However, the least rainy season is summer.
Here is the average precipitation.
Average precipitation - Melbourne
MelbourneJanFebMarAprMayJunJulAugSepOctNovDecYear
MelbourneJFMAMJJASONDY
Prec. (mm)504555605555505060706060670
Prec. (in)21.82.22.42.22.2222.42.82.42.426.4
Days6569101011121110108108

Although it has a mild climate, Melbourne is subject to temperature swings, because it can be reached both by cold air masses from the sea surrounding Antarctica, and by hot and dry air masses from the Australian desert.
The wind is quite frequent, since the westerlies regularly blow for most of the year, while in summer, when the weather is sunny, the sea breeze blows in the afternoon. Not coincidentally, around Melbourne there are several beaches frequented by surfers.
Winter, from late May to August, is mild, but also quite windy (the wind can increase the feeling of cold), and with quite frequent rains. However, between a disturbance and the other there may also be some sunny days. The average temperature of the coldest month, July, is 9.5 °C (49 °F). Very cold days are rare: at most, the night temperature can drop to the freezing point.

Spring, from September to November, is initially cool, and then becomes progressively milder. Due to clashes between air masses, spring is a quite rainy and windy season.

Summer, from December to mid-March, is pleasantly warm, since the maximum temperature is usually about 24/26 °C (75/79 °F). Nights are still cool, actually they can sometimes be a bit cold, since lows can drop to 8/10 °C (46/50 °F). The sun often shines, the wind blows frequently, and although it is the least rainy season, low pressure systems can still pass, bringing rainfall, besides some short thunderstorms can break out.
Although normally the summer is not hot, and sometimes can be cool, at times there can be heatwaves, when the winds blow from the north, ie from the red-hot Australian desert. At best the temperature remains about 30/35 °C (86/95 °F), otherwise it can sometimes exceed 40 °C (104 °F). For example, in January 2014, the temperature exceeded 40 °C (104 °F) for 5 days, of which 4 days in a row, with a maximum of 44 °C (111 °F), but few days before the heat wave, the minimum temperature was 8 °C (46.5 °F), and a few days later is dropped again to 10 °C (50 °F), confirming the fact that these heat waves are short hot periods in a climate that for the rest is mild.

Autumn, from mid-March to late May, is mild, and becomes progressively cooler and rainier over the weeks. As usual, there's no shortage of windy days, and at night it can get a little cold, since the temperature can drop below 5 °C (41 °F).

The amount of sunshine in Melbourne is better in summer, from December to February, when sunny days are quite frequent, while in the rest of the year it's just adequate, because as we said, weather disturbances often pass. In winter there can also be a bit of fog.

Melbourne

The sea in Melbourne is never warm, actually it's cold most of the year, and only reaches 18/19 °C (64/66 °F) from January to March. In the closed and sheltered Port Philip Bay, however, in summer the sea is slightly warmer.
Here are the average sea temperatures.
Sea temperature - Melbourne
MelbourneJanFebMarAprMayJunJulAugSepOctNovDec
MelbourneJFMAMJJASOND
Sea (°C)181918171615131313141516
Sea (°F)646664636159555555575961

When to go

The best periods to visit Melbourne are spring and autumn, namely the months of April-May and September-October: in this way you will avoid the hot summer periods, which, however, hit the city for a few days per year. It must be said that spring and autumn are quite rainy and windy. If it wasn't for the risk of scorching heat, summer would be preferable, from December to March. November can be an interesting month, at the end of spring: it's pleasantly warm, mostly sunny, with a lower risk of heat waves than in summer. However, even in summer there can be a bit of cool weather, or even cold, in the evening and at night, so it will be useful to bring a sweatshirt and a light jacket.