If you think this summer has been cooler than usual in Melbourne, you're not imagining it. The city is having its coolest summer in 19 years based on daytime temperatures.

The city's average maximum temperature during the first two months of summer were both about one degree below the long term-average.

Combining the average maximums from December (22.9ºC) and January (25.2ºC), Melbourne's running average for the first two months of the season was just below 24.1ºC. This is the city's lowest December-January average maximum temperature since 23.3ºC in 2001/02.

While one degree below average might not seem very impressive, it's worth noting that cooler-than-average summer months are hard to come by in the modern climate.

In the 2010's, there were only three cooler-than-average summer months during the entire decade.

In the 2000's, warm summer months outnumbered cool summer months by 19 to 11 and in the 1990's, it was 16 to 11.

Image: A comparison of Melbourne's summer months, per decade, based on mean maximum temperature. The blue bars show how many individual months in that decade were cooler than the long-term average. Red lines show how many summer months per dacade were warmer than the long-term average.

In fact, the graph above shows that all but one decade since the 1960's have had more anomalously warm summer months than cool summer months. Prior to that, cooler summer months either equalled or outnumbered warmer ones for every decade since Melbourne's records began in the mid-1800's.

It's no secret that no two months are the same in Melbourne, but the last two months have been pretty cool by modern standards.