With regard to rainfall, during the summer months, San Francisco is practically rainless. By referring to the accompanying charts it will be seen that in June, July, August, and September showers are very rare. The average rainfall is about 23 inches, and most of this falls during the months of November, December, January, February, and March. Looking over the records of the past fifty years we find that the year 1898 had but 9.31 inches, while in 1883 there was 38.82 inches. In 1861 there was 38.51 inches.

SEASONAL RAINFALL.

The annual rainfalls do not, however, fairly represent the amount of rainfall determining crop yield. Both with fruits and grains it is the seasonal rainfall rather than the annual which is to be considered. In the wheat fields summer fallowing is resorted to chiefly for the reason that the rain of two seasons can be utilized. As may be seen by the tables of annual and seasonal rainfall, published in following pages, the amounts during the growing season vary from the totals for the calendar year; thus, in 1889-90 the seasonal rainfall was 45.85 inches. The annual rainfall for 1890 was but 25.43 inches, an unusually heavy rainfall in December, 1889, having contributed to materially increase the seasonal amount.

Frequency as well as intensity should also be taken into account in considering the relation of rainfall and crops.

AVERAGE TEMPERATURE (DEGREES FAHRENHEIT) FOR EACH HOUR OF SEVENTY-FIFTH MERIDIAN TIME.

January.

February

March

April

May

June.

July

August.

September...

October..

November

December

Year..

.....

55.5

54.9

49.5

48.8

53.9

53.3 52.8

51.7

50.1 49.8 49.2 49.0 48.5 48.2 48.2 48.8 48.2 47.6
52.0 51.3 50.9 50.7 50.0 49.6 49.5
49.9 49.0 48.6
52.8 51.8 51.4 50.7 50.6 50.4 50.1 51.2 50.2
51.4
51.1
50.6 50.3 50.1
49.7 49.4 50.1 49.1 49.8 51.5 53.4
53.9 53.3 52.7 52.3 51.8 51.5 51.5 52.2 51.2 53.2 55.4
54.4 53.6 53.1 52.7! 52.4 52.1 52.0 53.1 52.5 54.0 55.8 56.8
53.8 53.6 53.5
53.11 52.8 52.6 52.6
53.5 52.4 54.7 57.1 59.0
56.8 56.4 56.0 55.7 55.1 54.9 55.1 55.8 54.7 55.6 57.5 59.4
60.0 59.3 58.8 58.5 58.1 57.9 57.6 58.7
57.4 58.5 60.5 62.5
56.1 55.8 55.1 54.6 53.9 53.7
53.5 54.7 53.5 53.9 55.2 56.5
54.2 54.0 53.3 52.9 52.4 53.9 52.5 52.0 52.6 54.1
48.2 47.5 47.1 46.9 47.1 48.4 47.2 46.9 47.1
52.4 52.0

AVERAGE TEMPERATURE (DEGREES FAHRENHEIT) FOR EACH HOUR OF SEVENTY-FIFTH MERIDIAN TIME-Continued.

57.9 59.3

60.1

60.4

58.0 59.2 60.1 60.1 59.6
52.0
52.9 53.6 54.0 53.3 52.8 52.5 51.6 50.8 50.0 49.8 55.1 45.4
60.1 59.0 58.2 57.1 56.0 55.1 54.5 55.2 62.1 50.4

58.7 57.9 57.2 56.6: 56.0 55.7 62.2 50.4

AVERAGE PRESSURE (INCHES AND THOUSANDTHS) FOR EACH HOUR OF SEVENTY-FIFTH MERIDIAN TIME.
[A-37° 48′ N.; p. 122° 26′ W.; local time, 3h 10m slow. H==155 ft.]

January
February

March.

April

May.

June

July

August.

September...

October

November..

December

0.062 0.048 0.035 0.025

0.023

0.023

0.021
0.999 0.981 0.971 0.968 0.970 0.968 0.974 0.981 0.986 0.992 0.984 0.048 0.930
0.035 0.020 0.002 0.985 0.977 0.972 0.968 0.972 0.78 0.981 0.988 0.998 0.062 0.935
0.903 0.895 0.881 0.867 0.857 0.850 0.845 0.847 0.852 0.864 0.839 0.872 0.922 0.820
0.870 0.864 0.856 0.847 0.837 0.831 0.828 0.827 0.829 0.842 0.851 0.846 0.893 0.798
0.875 0.869 0.861 0.855 0.846 0.838 0.833 0.830 0.832 0.840 0.852 0.854 0.901 0.809
0.828 0.824 0.818 0.810 0.802 0.794 0.786 0.783 0.787 0.793 0.804 0.807 0.846 0.765
0.775 0.772 0.764 0.754 0.742 0.733 0.723 0.723 0.728 0.733 0.741 0.745 0.785 0.707
0.834 0.827 0.819 0.812 0.802 0.792 0.787 0.782 0.783 0.789 0.798 0.806 0.848 0.759
0.826 0.818 0.808 0.794 0.784 0.777 0.773 0.777 0.781 0.789 0.796 0.801 0.847 0.747
0.891 0.883 0.868 0.855 0.849 0.844 0.840 0.844 0.850 0.859 0.866 0.864 0.913 0.812
0.927 0.913 0.900 0.889 0.883 0.879 0.879 0.884 0.890 0.893 0.898 0.898 0.961 0.837
0.025 0.029 0.035 0.039 0.044 0.041 0.097 0.991
0.855 0.856 0.860 0.867 0.872 0.876 0.927 0.826

a From observations at 8 a. m. and 8 p. m. 76th meridian time. Local mean time 3 h. 10 m. slow.