ut the greater
part of the country is north of the Tropic of Cancer. Except a narrow
belt on the north along the Mediterranean shore, Egypt lies in an
almost rainless area, where the temperature is high by day and sinks
quickly at night in consequence of the rapid radiation under the
cloudless sky. The mean temperature at Alexandria and Port Said varies
between 57 deg. F. in January and 81 deg. F. in July; while at Cairo,
where the proximity of the desert begins to be felt, it is 53 deg. F.
in January, rising to 84 deg. F. in July. January is the coldest
month, when occasionally in the Nile valley, and more frequently in
the open desert, the temperature sinks to 32 deg. F., or even a degree
or two below. The mean maximum temperatures are 99 deg. F. for
Alexandria and 110 deg. F. for Cairo. Farther south the range of
temperature becomes greater as pure desert conditions are reached.
Thus at Assuan the mean maximum is 118 deg. F., the mean minimum 42
deg. F. At Wadi Halfa the figures in each case are one degree lower.

The relative humidity varies greatly. At Assuan the mean value for the
year is only 38%, that for the summer being 29%, and for the winter
51%; while for Wadi Halfa the mean is 32%, and 20% and 42% are the
mean values for summer and winter respectively. A white fog, dense and
cold, sometimes rises from the Nile in the morning, but it is of short
duration and rare occurrence. In Alexandria and on all the
Mediterranean coast of Egypt rain falls abundantly in the winter
months, amounting to 8 in. in the year; but southwards it rapidly
decreases, and south of 31 deg. N. little rain falls.

Records at Cairo show that the rainfall is very irregular, and is
furnished by occasional storms rather than by any regular rainy
season; still, most falls in the winter months, especially December
and January, while, on the other hand, none has been recorded in June
and July. The average annual rainfall does not exceed 1.50 in. In the
open desert rain falls even more rarely, but it is by no means
unknown, and from time to time heavy storms burst, causing sudden
floods in the narrow ravines, and drowning both men and animals. These
are more common in the mountainous region of the Sinai peninsula,
where they are much dreaded by the Arabs. Snow is unknown in the Nile
valley, but on the mountains of Sinai and the Red Sea hills it is not
uncommon, and a temp