It's May 4 at 2pm, and the temperature here is a very unseasonable 39.7° with a midnight high of 41.5°! Nevertheless, hot weather will be here again soon, so this has been today's project based on this presumption.
From May 1 to September 30 the Weather Prediction Center generates heat index outlook maps for 3 to 7 days ahead. This script initially displays a set of maps without a threshold applied. From there a dropdown menu allows the viewer to select map sets with a threshold of from 95° to 115° in 5° increments. At 895 pixels the width of the map set is quite large, but must be maintained in order to preserve the correct geometry for the city links' functionality--sorry about that.
Edit 2013 August 24: I've revised the NWS Heat Index Map display scripts by using jQuery's AJAX 'load' to re-display only the portion of the page that changes with a new Heat Index Threshold selection. In other words it uses partial page loads rather than full page reloads. This has reduced the number of files in this package from fourteen to three, improved load times, and greatly reduced bandwidth consumption. You can check it out
here on my site. This version replaces all prior versions.