The Natural History of Foster City, California
by James K. Sayre
a draft manuscript
12 May 2005
Chapter 4 - The Bay, Weather, Air Quality, Foster City's very own Weather Station, Tides, The Night Skies, Tsunamis, Noise and Airplanes
.c.The Bay
The San Francisco Bay is a grand creation of Nature in the rather recent (geologically speaking) past. As the last Ice Age ended, the sea levels around the world rose. The low point of the California coastline, where the Golden Gate is now located, was breached by the Pacific Ocean and the then-extant river valley was flooded. This began happening about 10,000 years BP (Before Present). The Bay reached its maximum size just before the arrival of white man. Today, the Bay water surface area has been greatly reduced by the filling of the marshlands and mudflats along its edges.
The Bay moderates the inland climates of the Bay Area to a great extent. One only needs to compare the Bay Area climates to that of areas that are inland the same distance from the Pacific Ocean elsewhere in California. For example, Ukiah, a small city in northern California, located about twenty-five miles inland behind the coastal range, averages a maximum temperature of 91.2° F for the summer months of July, August and September [Felton]. Paso Robles, a small city in southern California, located about twenty miles inland averages a maximum temperature of 91.6° F for the same period. By contrast, summer average maximum temperatures for cities moderated by the San Francisco Bay are much lower. San Francisco's average daily maximum temperature over the same summer period is 66.1° F; Oakland's is 72.4° F (measured at the Oakland International Airport) and the San Francisco's International Airport averages 72.4° F [US NOAA]. Clearly, proximity to the Bay greatly moderates the summer maximum temperatures in comparison to other inland areas. The region next to the Bay has a climate greatly moderated by the lagging effect of the large body of water on the temperatures in both in the summer and winter seasons. The summer temperatures are lower, cooled by the Bay waters and the winter temperatures are warmer, being heated by the Bay waters. For example the average winter minimum temperatures, measured in December, January and February for Ukiah is 35.3° F; in Paso Robles the average winter minimum temperature is 33.7° F. In the three locations Bay Area locations moderated by the Bay waters these average winter minimum temperatures are several degrees higher. For Oakland it is 40.7° F, while for San Francisco it is 46.2° F and for the San Francisco International Airport it is 42.6° F.
End.
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