Published Tuesday, February 20, 2001 in the San Jose Mercury News


Weather plays part in your utility costs

Special to the Mercury News 

With the exception of political ineptitude and possible price gouging, few factors affect your utility bill as much as the weather.

Most utility companies either have meteorologists on staff or contract with outside meteorological firms to monitor and forecast a variety of weather phenomena. Tops on the list of meteorological importance for most gas and electric companies are forecast temperatures.

Not only are the maximum and minimum temperature readings crucial, but so are the temperatures at other critical times of the day when energy usage is directly related to thermometer readings. For example, on a chilly morning, not only are heaters turned up a notch, but you might take a slightly longer hot shower or have a warm breakfast instead of a cold one. All these things use extra kilowatts.

By having advance notice of these temperatures, the utility companies can arrange for enough power to meet everyone's needs.

Utilities also monitor the temperatures in other parts of the country to be able to purchase enough gas and electricity from other regions in a timely and economical manner.

Here in the West, where hydropower is key to the energy picture, the utilities keep close tabs on both the rain and snowfall. This allows them to determine the amount of runoff that will be available to run the power plants throughout the year. Many utilities also have cloud-seeding programs to enhance rainfall, even if only slightly.

Q. Is there a way to find average temperatures for a particular span of time? As you might guess, I am looking at my PG&E bill for Dec. 20, 2000, to Jan. 21, 2001. We were trying to cut back on the thermostat, but in spite of that we used an average of 4.7 therms per day this year compared to 3.5 last year. The year before that we used 5.1 therms per day. I do have the impression that it's been colder this year, but I'd like some hard data. Was January 2000 particularly warm, or January 2001
particularly cold?  Ann Turner - Menlo Park

A.  This is certainly a timely question, as I just got my bill too.

Instead of average temperature, the best guide is a statistic called a heating degree day (HDD). This tells how many degrees the daily average temperature is below 65 degrees, and relates well to energy consumption.

For example, if the high and low temperature for a given day are 60 and 40, respectively, the average daily temperature would be 50 degrees and there would be a total of 15 degree days for that day. The heating degree days are then summed up for the month. The higher the HDDs, the higher your heating costs are likely to be.

Here are some HDD figures for San Jose that indicate temperature patterns. In January 2000, the average HDD was 377. In January 2001, it was 493. The 30-year average HDD for January is 484. Based on these figures, it appears that this past January was colder than normal, and much colder than the year before.

Q.  I had once heard the expression ``Red sky at morning, sailors take warning . . . red sky at night, sailors delight.'' Some of the Bay Area's most spectacular sunrises are just before or during storms, as compared to our normal fiery Pacific sunsets, and I think there might be some truth to this saying. But I have to believe that this is very specific to a few oceans, a few coasts and perhaps one hemisphere. Do you know where this saying originated and where they were referring to? David Moss - Palo Alto

A.  The first reference I can find is the Bible in Matthew 16:2-3, which says ``When evening comes, you say, `It will be fair weather, for the sky is red,' and in the morning, `Today it will be stormy, for the sky is red and overcast.' ''

This and the more common phrase you cite do have some basis in fact. Since most weather systems come from the west, clear skies to west at sunset indicate that no bad weather is coming. In the morning, if the red sunrise is visible to the east, there is an assumption that skies may cloud up from the west.

Another variation is: ``Evening red and morning gray, help the traveler on his way. Evening gray and morning red, bring down a rain upon his head.''

Q.  Why are blizzards and Nor'easters impossible in the Bay Area? Are Pacific Ocean waters too warm? Jacob Wang - San Francisco

A.  You are absolutely correct in guessing that the relative warmth of the Pacific waters is the reason. The trajectory of most storms that reach California is from the west or northwest. This makes the storms relatively warm and moist compared to storms that originate in Canada.

These cold Canadian air masses can become particularly intense blizzards as they pick up moisture from the Great Lakes or spin off the New England coast as a Nor'easter.

Jan Null, founder of Golden Gate Weather Services and Director of M eteorology for, is a retired lead forecaster with the National Weather Service. Send questions to him c/o WeatherCorner, San Jose Mercury News, 750 Ridder Park Drive, San Jose, Calif., 95190. You also can telephone and fax questions at (510) 657-2246 or e-mail them