G. Moxon's Humidity Data for Fallbrook, CA

T. Chester and G. Moxon

G. Moxon uses an automated weather station to accumulate Fallbrook weather statistics at his location in north Fallbrook every 30 minutes since 1993. T. Chester has computed the maximum and minimum humidity for each day. Those individual values are plotted below, followed by plots of the median maximum and minimum humidity computed from a 15-day running median average, 7 days before a given date and 7 days after, using all recorded years.

The plots are all scaled from 0 to 100 for easy intercomparison, and 1.5 years are plotted to easily see any seasonal variation.

(Click on graph for bigger and better image.)
Color code

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We don't know of any reference source that could be used to validate these humidity measurements. However, it is reassuring that the peak humidity reaches 99% on most days, since Fallbrook is in an ocean-dominated climate about 85% of the time, and a peak humidity of 99% is practically the definition of such a climate.

The median low humidity of about 40% also seems reasonable. It would be nice to validate that the infrequent readings below 10% also represent a reasonable extreme level of humidity. If any reader can validate that or disprove that, please email one of us.

The color code for individual years is as follows:


Summary of Fallbrook's Humidity Variation

The median peak humidity is 90-95% every day of the year except in November and December, when it goes as low as 60%.

The median low humidity is ~40% every day of the year except in November and December, when it goes as low as 20%.

Low daily humidities (peak daily humidities below 50%) essentially only occur in October through March, but are infrequent enough to be almost entirely absent from the median humidity plots except at their peak occurrence rate in the last 1.5 months of the year.

Low humidities usually coincide with a "Santa Ana" condition, when the prevailing wind in Fallbrook shifts from southwesterly to another direction. Southwesterly winds of course come from the ocean and bring the usual high peak humidity condition of Fallbrook.

Wintertime has the most extreme range of humidities, ranging from very low Santa Ana values to very high on days with rain.

The evenness of our May through September climate is well-shown on the plot of individual minimum humidity values, when the variability of the minimum humidity is quite small during those months.

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Copyright © 1997-2000 by Tom Chester and Gaylord Moxon.
Permission is freely granted to reproduce any or all of this page as long as credit is given to us at this source:
Comments and feedback: Tom Chester | Gaylord Moxon
Last update: 14 June 2000.