MONTHLY SUMMARY 



December 1940 



Normal 



Extremes 



Barometer, in inches 



(Readings reduced to sea level) 



Maximum 30.64, 19tli 



Minimum . 29.44, 30th 



Mean semi-daily 30.063 



Range 1.20 



Air Temperature, in degrees F. 



Highest 47, 25th, 27th 



Lowest -10, 4tb 



Mean 29.4 



Range 57 



Highest mean daily 40.5, 27th 



Lowest mean daily 6.5, 4th 



Mean maximum 37.9 



Mean minimum 20.9 



Greatest daily range 33, 4th 



Least daily range 3, 28tli 



Precipitation, in inches 



Precipitation 301 



Snow 5.00 



Maximum precipitation in 24 hrs. 1.00, 28th 



Number of days with .01 or more 11 



Wind, in miles 



Total movement 3560 



Greatest daily movement 307, 21st 



Least daily movement 31, 15th 



Mean hourly velocity 4.8 



Maximum velocity 28, 3rd, 31st 



Wind, direction 



Prevailing direction NVV 



North, days 10 



Northeast, days 



East, days 



Southeast, days 3 



South, days 6 



Southwest, days 1 



West, days 1 



Northwest, days 10 



Weather 



Mean relative humidity, percent 79.6 



Mean cloudiness, percent 62 



Number of clear days 10 



Number of fair days 7 



Number of cloudy days 14 



Number hours bright sunshine 109 



Percent of possible hours of bright 

 sunshine 38.9 



30.66 



29.27 



30.06 



1.38 



54.3 

 -1.9 

 27.5 

 56.2 



3.39 

 8.50 



10 

 4710 



6.3 

 31.4 



WNW 



69.4 



54.9 



8 



9 



14 



128 



45.2 



30.96, 1889 

 28.85, 1915 



1.78, 1895; 1.01, 1892 



65.5, 1908 



-22.5, 1917 



36.9, 1891; 17.1, 1917 



7.77, 1901; .87, 1896 

 26.50, '02; t, 1891 



17, 1902; 4, 1892 

 6,694, 1925; 3,239, 1918 



48, 1938 



71, 1929; 39, 1919 



15,1890; 2, 1922,1933 



16, '09; 4,'89 '30, '31,'36,'38 



23, '33; 7, '09, '23 



172, 1896; 63, 1933 



Note — The first column in the above summary gives observations made during the 

 month. The second column gives the averages based on observations made from 

 1889 to 1938, except that humidity records are based on observations made from 

 1929 to 1938. The third column gives extremes observed from 1889 to 1939. 



