Topic: Historical weather temperatures and graphing

[camplate]

If there is a textbook I can read that would better answer what I am thinking point me in that direction.
This will be a stream of consciousness post. I don't know exactly what I want and I know it doesn't matter.
When the daily average temp is given, is it generally an average of the last 30 years, updated each 10 years? Also averaged over a span a days, like if a day is a degree colder than the surrounding days the average for that day will be listed as the average of the other days.
Also assume that weather is dumb downed for the masses. (dumbed isn't a word?)
What I'd like to see or create would be a graph that has the average high and low temp for each day, over thirty years, and the standard deviation for each day.
Would standard deviation be the best thing to graph?
And I have no idea where the temperature data is stored. Once I was able to download historical data for a large city but I haven't seen that in years.

Look forward to any discussions. Thank you for reading.

Edit: https://www.weather.gov/mkx/monthly_climate_table I found this graph which is close to what I want to create.

[bchwdlks]

The data that you are searching for (if for USA) is probably available at NOAA Climate Data Online web site.
To get the raw data, you will have to specify location, date range and what type of weather data you want. The results will be sent to you via email in a pdf or csv file. You can use that data to generate the graphs and charts that you want.

Every time I have requested historical data, I have received the data within an hour. But the disclaimer always says it can take up to 24 hours to get the results. The site above is just one section of National Centers for Environmental Information. The NCEI is the repository for ALL the climate/environmental data that the US Government has collected.