[R] Plotting weather data

[Rachael Howard]

Hello.  I am relatively new to R and trying to figure out how go about  
graphing something like this:  http://www.math.yorku.ca/SCS/Gallery/images/NYweather.jpg

Specifically, I am having a hard time graphing the mean, min, and max  
temperatures as they are depicted on that graph. When I plot the same  
data using plot(Date,Mean_Temperature, col="black", type="line"), the  
lines are all over the place, instead of neatly arranged in that  
accordian-like manner.

Where should I start?