How to draw vertical lines on Highcharts graph?

I think you might be looking for Plot Bands and/or Plot Lines.

Here's some more information:

http://www.highcharts.com/docs/chart-concepts/plot-bands-and-plot-lines

You will most likely have to use the Highcharts renderer for this task, as what you want to do doesn't quite fit in with a grid, and doesn't quite fit in with plot lines.

I have made a very simple example, based on your code which shows drawing an arbitrary vertical line, in a hard-coded location. To achieve your goal you will have to calculate a few things, such as the x/y position for the start point of each line, and the height of the line based on that points value.

Here's a slightly different example with zIndex and a line as you actually want it, using the V path command to draw a vertical line.