Canberra frosts
Each bar above is one year's frost season at Canberra Airport, from the first night the temperature fell to 2 degrees or below to the last (2 degrees is an accepted proxy for freezing ground conditions). Darker bars are years that had more frosty nights. You can hover over or tap a year for data.
I first examined these data years ago for an article on winter folklore. I've since used them to teach students about hypothesis testing, such as the claim that Canberra's frost patterns are changing.
What's clear is a slight trend in recent years towards milder, shorter frost seasons that start later and end earlier. However, the data don't demonstrate statistically significant change in this centry's frost seasons compared with last century's – annual aggregations like this as are the wrong metric to map out that kind of change.
N.B. These data combine airport measurements collected since September 2008 with a comparison dataset the Bureau of Meteorology developed for earlier dates.
I built this with D3.