The existing Javascript graphing libraries have been really slow for the quantity of weather data we're dealing with. With more than one temperature sensor the Javascript takes a long time especially on older tablets. All the data has to be first loaded to the tablet and Javascript would convert that into a SVG (Scalable Vector Graphics).
In looking around at other options we decided it would be best if the Raspberry Pi generated the SVG and the table only has to render the SVG.
This new system doesn't need to reload the entire graph for each update, it only gets the latest updates from the Raspberry Pi and updates the graph. Now the graphs load quickly and update quickly.