over 1 year ago - Shurenai - Direct link
Activity heat != Temperature heat.

Activity heat is like a keyboard heatmap- A keyboard heat map shows how often a given key is being struck compared to others

Example:
https://www.bypeople.com/wp-content/uploads/2015/05/keyboard-characters-distribution-heatmap.png

It's referred to as 'heat' and 'temperature' because of the color coding used; ranging from cool blues to red hots for least to most activity, just like temperature is shown on the news/weather.