Complex sentence: Temperatures exceed on around 20--25 days a year but over the last few years have exceeded this number substantially, the average maximum temperature is in the summer, and overnight is around, the mean annual rainfall is.
Split into simpler sentences: Temperatures exceed on around 20--25 days a year but over the past few years have exceeded this number substantially. The average maximum temperature is in the summer, and overnight is around, the mean annual rainfall is.