I have a algorithm for detecting summer. Seven consecutive days in a row with a temperature of or above 20 degrees Celsius. I give you Summer, from the Bureau's seven day forecast for Melbourne:
Thursday Fine. Min 6 Max 21 Friday Mainly fine. Min 12 Max 25 Saturday Fine. Min 12 Max 30 Sunday Shower or two. Min 15 Max 22 Monday Fine. Min 10 Max 23 Tuesday Fine. Min 12 Max 28
I swear, this gets earlier and earlier each year.