High and Low Temperature Averages For Fallbrook, CA

Plots Of High And Low Temperatures, All Measurements And Median Averages

The following plots use the temperature data I have been collecting since 25 September 1994 (more info). I calibrated those temperatures to the official Fallbrook temperatures to remove the biases of my data.

All individual temperature measurements are shown in the plots on the left. A 31-day running median average is shown in the plots on the right. (A median is the value in the middle of a sorted list, so on average, half of all temperatures during a month will exceed the quoted median, and half will be below that value.)

Most of the bumps and wiggles on the median average plots probably result from averaging only 3 years of data. All plots span 1.5 years to easily see the seasonal variation.

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

(Click on graph for bigger and better image.)

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

(Click on graph for bigger and better image.)

The color code for individual years is as follows:

The following table gives the median monthly values of the temperatures, which are the values given in the median plots above for the middle of each month. In addition, the median value of the percentage of possible sunshine is given.

The plots below give the distribution of all measured temperatures, highs on the left and lows on the right. The histograms are in units of fraction of all measurements. Hence from the plots you can deduce that:

• High temperatures over 100° F. occur on much less than 1% of all days;
• High temperatures over 90° F. occur on about 12% (~8.5 + 3.3 + 0.3) of all days;
• High temperatures below 60° F. occur on about 5% (~3.5 + 1.2) of all days;
• Low temperatures below 40° F. occur less than 5% of all days; and
• Low temperatures below 35° F. occur less than 0.5% of all days.

(Click on graph for bigger and better image.)

(Click on graph for bigger and better image.)

The plots below give similar histograms for each month. Each plot combines four months, with each month color-coded. The first color on the left corresponds to the first month listed in the title. As an example of reading one of the plots, here are some conclusions from the high temperature plot for July and August. July is the month on the left of the "July, August, September, October" plot below, graphed in blue, and August is the 2^nd month from the left, graphed in green:

• For July, no high temperatures below 75° were recorded by me at all;
• About 7% of all high temperatures in July are above 95°; and
• About 15% of all high temperatures in August are above 95°.

The average peak summer temperature occurs on 28 August, plus or minus a week.

There is a slow rise toward the peak average summer temperatures, both for lows and highs, but a sharp fall toward the winter temperatures.

The lowest average temperatures (lows below 50° and highs below 75°) occur from the middle of November to the middle of April.

There is a huge variability in the high temperatures. A high of 90° can occur on any day of the year. A high of 100° can occur on any day from May through October.

Low temperatures are much less variable, with the highest variability in the winter associated with rainstorms.

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Copyright © 1997, 1998 by Tom Chester.
Permission is freely granted to reproduce any or all of this page as long as credit is given to me at this source:
http://sd.znet.com/~schester/fallbrook/weather/tjc/temps.html
Comments and feedback: Tom Chester
Last update: 2 January 1998.