Exactly this plus with only showing years and temperature you're forcing a 2 variable data set onto a heatmap which is best for 3 variable data. Showing months as the third variable would be much more intuitive and could show interesting trends like more/variation between months and stuff.
_skjold_ t1_iztqpsp wrote
Reply to comment by sprcpr in [OC] Yearly Average Temperature in the UK, 1884 - 2021 by PieChartPirate
Exactly this plus with only showing years and temperature you're forcing a 2 variable data set onto a heatmap which is best for 3 variable data. Showing months as the third variable would be much more intuitive and could show interesting trends like more/variation between months and stuff.