The problem with weather date, of course, is that there's so darn much
of it. The biggest challenge has to do not only with finding the
right source, but then figuring out how to massage the raw data into
With a bit of persistence though, and a lot of wading through the NOAA
website, I finally found what I (you, actually) needed at the
following NOAA climate data site:
Global and U.S.--Select by Station (Integrated Surface Hourly)
This data set has historical hourly data records from thousands of
stations around the world.
By working my way through the options provided, I was able to access
(at no charge, as it turned out), the data for San Francisco
International Airport for all hourly temperature records for the month
of March for the period 1990-2006.
I took the hourly data for March for each year and averaged out the
temperatures for each hour; i.e., I added up all the data points for
noon temperature and found the average over the years...ditto for the
other 23 hourly periods.
The results are shown in a graph, here:
Hourly Avg Temp in March in SF
Click on the "Original Size" button to see it full sized.
I trust this graph is exactly what you were after.
However, please don't rate this answer until you have everything you
need. If you would like any additional information, just post a
Request for Clarification to let me know how I can assist you further,
and I'm at your service.
All the best, and thanks for a real challenge!