Temperature Statistics

Say I have daily climate records for December going back 100 years at a specific point on the globe.  What is the significance of doing the following:

A) Taking the standard deviation of all 31*100 points.

B) Taking the monthly means for each year, and then taking the standard deviation for each of those monthly means.

A would be the standard deviation of the daily temperature of December sampled over 100 years. 3100 samples.

B would be the standard deviation of the monthly average temperature of December sampled over 100 years.  100 samples.

i think the 3100 sample one should have a higher standard deviation.  since standard deviation is a measurement of average distance from the average, if i recall correctly.  so you could have huge variations in temperature within one month, whereas if you had averaged it for the month it's dulled down. 

essentially what i'm saying is that i'd assume the daily temperatures fluctuate more than the monthly averages.

I'm feeling really keen, for some of that good ol' green

Marijuana MUST be legalized.