[stoney]

When I used to work in building design, I used to create lots of charts of various climate data for projects in new regions where I didn't know much about the climate (and also for eye candy in presentations). One of those charts was very similar to what you suggested. Basically a 2D array of coloured squares, with hour of the day along one axis and month of the year along the other. Then each square would be coloured according to the average solar radiation falling at that time of day in that month (using a blue-green-red type scale usually, but you can do grey scale or anything else you can think of). It was a useful way of visualising lots of stuff - variation in day length, strength of the sun, summer/winter variations, etc.

You can plot other variables like this too - temperature, humidity, ...