THE WEATHER 161 



year; while the growing season is from November to 

 May. In summer the storms entering British Colum- 

 bia from the west pass so far to northward that they 

 do not touch California, but in winter they pass farther 

 south and so give us our winter rains. This is shown 

 in the two storm tracks in figure 79. 



Along the coast from Santa Barbara to Cape Mendo- 

 cino, in July and August, there are heavy fogs, only from 

 fifteen hundred to two thousand feet in height (figure 

 81), caused by the moist and warm air from the sea cross- 

 ing the cold water current which comes down along the 

 coast from the north. Above these cool fogs the air is 

 warm and clear, and the fog quickly dissolves as it 

 reaches the warm air which prevails all summer in the 

 Great Valley. But so long as these fogs come through 

 the Golden Gate with a west wind, no rain need be 

 looked for, however dark the sky. The hot air of the 

 Great Valley, rising on the Foothill slopes, causes the 

 indraught through the Golden Gate and over the Coast 

 range. This in the Sacramento Valley causes a south 

 (up-valley) wind, in the San Joaquin Valley a north 

 wind (in this case also up-valley), which cools the after- 

 noons. In winter heavy wet fog sometimes covers 

 the Great Valley for weeks. 



At irregular times, hot, dry north winds (northers) 

 sweep over the whole of California in summer, doing 

 damage to crops. They seldom last more than three 

 days. Similar winds in winter are very cold. 



