Here I have generated histograms by month of the maximum temperatures of my home city Melbourne (Australia) for the forty-year period of 1971-2010. The temperatures are collected into temperature bins of size 2 degrees Celsius. The most frequent temperature range is 14-16°C in the cooler months (June-Sep) up to 20-22°C in the warmer months (Dec-Mar). The moderating influence of the Southern Ocean is the primary cause of this relatively small difference. However in the summer months hot winds from the interior of the continent skew the distribution and push the mean maximum closer to 25°C. Curiously in January the maximum has been as likely to be 36-38°C as 30-32°C.
One can see how bunched up the maximum temperatures are in the winter (never too cold) compared with the summer (sometimes too hot!). Since the data is collected over a forty year period, simply divide the y value by 40 to see how many days per month one achieves a particular range. For example, in the month of May between 8 and 9 days per month the maximum temperatures has been between 16 and 18°C.
Here we see the most common range is 14-16°C which has happened about 57 days per year (47 of these between May and Sep) and 81% of the time it has been between 12 and 26°C (and 17% of the time above 26°C). The overall range is 7.0 to 46.4°C. On average the maximum temperature has exceeded 40°C 1.5 times per year and been less than 10°C 0.8 times per year.
The data for this post comes from http://www.bom.gov.au/climate/data/.