Change of Temperature with Distance from Coast in San Diego County, CA

A real estate agent from Vista, Alice Gieseler of Century 21 in Vista, said "The climate in Vista is unbeatable. We have the sun and ocean breeze without the fog. And we don't have the unbearable heat like Escondido and Fallbrook," as reported in the North County Times on March 17, 1997, p. B-4. That led me to investigate just what the real difference in high temperature is between Vista and Fallbrook.

The leftmost plot below shows the high temperatures during the recent heat spell of 18-20 March 1997 for the official high temperatures for various cities, plotted versus the distance from the coast. Each day is represented by a different symbol.

(Click on graph for bigger and better image.)

(Click on graph for bigger and better image.)

On the rightmost plot, I added data from the heat wave on 27-29 May, 1997, which probably was a typical summer heat wave (but not a Santa Ana). In order to take out some of the variation with day, the plot shows the {change in temperature relative to the Oceanside Pier temperature} versus distance from the coast for all available data for all six days (18-20 March and 27-79 May 1997) . Again, each day is represented by a unique symbol. Because some of the temperatures were not reported on some days, some points are missing for some cities on some days.

Here are the values for the high temperature in Fallbrook and Vista for the March and May heat wave days, which can be used to identify the different days in the plots above:

 High Temperature 

Note that on one of the heat wave days, the Vista temperature was higher than that of Fallbrook! The average difference in high temperatures is 2.2o, which is a pretty piddling difference.

An independent way to check what the difference in high temperature should be can be obtained from Weather of Southern California by Harry P. Bailey, University of California Press, 1966, by using Fig. 5 on p. 21, which gives the increase of temperature with distance inland on an average summer afternoon. The Vista weather station is 7 miles from the coast, and the Fallbrook weather station is 14 miles from the coast. That distance should translate into an average high difference of 5°, not far from the 3-4° found above. A difference of 5° is certainly significant, but far from a difference between "unbearable heat" and "a perfect climate".

Furthermore, Vista actually extends from 4 - 9 miles from the ocean, and Fallbrook extends from 12-18 miles from the ocean. Thus the difference in average summer high temperature between the farthest edge of Vista from the ocean and the closest part of Fallbrook to the ocean is negligible.

The plot above can be used to roughly predict what the average high temperature in the summer would be for another location by correcting for the difference in the distance to the beach between that location and my house.

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Copyright © 1997-2002 by Tom Chester.
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Last update: 29 May 2002.