in the advanced graphs,weather data section, you can select to plot lots of different data, and set to be auto scale
I could add in auto scale all, and add in option to plot heat index (and then I guess windchill)
and also the extra sensor/custom graph in the advanced graphs you select to plot lots of different things (like heatindex/humidex, windchill)....but I would need to add in auto scale option..
but
note that you can use the customise setup in the auto scale graphs, and select to plot heatindex against temperature
I would need to add in option for longer period plotting (month to date and year to date)