Ideally, the normal high and low temperatures, humidities, precipitation, winds and other normalized data are calculated based on years of climate data. WeatherCurrents.com does not yet have years of climate data for any of its sites (currently there are four and a half years of temperature data, three years of rainfall data, and over two years of humidity, wind, and barometric pressure data for Temecula, and only a month of data for Murrieta) to produce a completely accurate result for normal conditions. The root problem is that one hot or cold spell or other unusual weather conditions in a period when there aren't many years of data can skew the calculated "normal" temperature, wind speed, humidity, rainfall, etc. so that it appears hotter or colder than it really is. Several more years of data will reduce the impact of abnormal weather conditions and offer a truer reading of what "normal" is.

As a prime example of this effect, consider Temecula's data from October, 1999 and October, 2000. October, 1999 was unusually warm, featuring several 100 degree days, one as late as October 30th. On average, October, 1999 was a full seven degrees warmer than October, 2000. Now, October, 2000 was likely cooler than a normal October. But do they even each other out? Probably not. Since then, October, 2001 featured temperature data in between October, 1999 and October, 2000. The totals for late October in particular will likely be skewed a little higher than the true norm for a few years to come.

Currently, the normal conditions that you see on WeatherCurrents.com are an 11 day moving average of the particular weather condition around and including the target date, for all of the years currently on record. For example, the normal high and low temperatures for February 15th would be computed by averaging all of the high and low temperature samples for February 10th through the 20th for all of the years in the archive. Averaging gives a nice seasonal sampling from many days of data surrounding the target date and reduces aberrations for a single date. If you visit these pages often, you will notice the normal highs and lows sliding upwards as you might expect in the springtime and decaying in the autumn.

Likewise, normal temperatures, humidities, and wind conditions for time of day are also computed using the same 11 day moving average. The difference is that the samples used for averaging to compute the normal condition are derived from the nearest sample to that time of day for each day used in the computation. Thus, a normal temperature for 2:00pm on February 15th, for example, would currently use the following 33 samples:

February 10, 2000	2:00 pm	59.6°F
February 11, 2000	1:59 pm	60.5°F
February 12, 2000	1:59 pm	61.0°F
February 13, 2000	2:00 pm	54.5°F
February 14, 2000	2:00 pm	65.4°F
February 15, 2000	1:59 pm	69.6°F
February 16, 2000	1:59 pm	55.3°F
February 17, 2000	1:59 pm	58.9°F
February 18, 2000	1:59 pm	70.5°F
February 19, 2000	1:59 pm	78.5°F
February 20, 2000	1:59 pm	59.6°F
February 10, 2001	1:59 pm	47.8°F
February 11, 2001	2:00 pm	59.0°F
February 12, 2001	2:00 pm	49.8°F
February 13, 2001	2:00 pm	52.1°F
February 14, 2001	2:00 pm	58.1°F
February 15, 2001	2:00 pm	66.4°F
February 16, 2001	2:00 pm	68.7°F
February 17, 2001	1:59 pm	65.3°F
February 18, 2001	1:59 pm	63.8°F
February 19, 2001	2:00 pm	62.1°F
February 20, 2001	2:00 pm	60.2°F
February 10, 2002	2:00 pm	69.9°F
February 11, 2002	2:00 pm	80.4°F
February 12, 2002	2:00 pm	79.8°F
February 13, 2002	2:00 pm	72.7°F
February 14, 2002	2:00 pm	67.9°F
February 15, 2002	2:00 pm	76.8°F
February 16, 2002	2:00 pm	64.7°F
February 17, 2002	2:00 pm	53.2°F
February 18, 2002	2:00 pm	58.2°F
February 19, 2002	1:59 pm	65.3°F
February 20, 2002	1:59 pm	73.8°F

Thus, the normal temp for 2:00 pm on February 15th is: (59.6 + 60.5 + 61.0 + 54.5 + 65.4 + 69.6 + 55.3 + 58.9 + 70.5 + 78.5 + 59.6 + 47.8 + 59.0 + 49.8 + 52.1 + 58.1 + 66.4 + 68.7 + 65.3 + 63.8 + 62.1 + 60.2 + 69.9 + 80.4 + 79.8 + 72.7 + 67.9 + 76.8 + 64.7 + 53.2 + 58.2 + 65.3 + 73.8) / 33 = 63.9°F.

Rainfall is entirely a different matter, and normal rainfall is not currently calculated at all on WeatherCurrents.com. This is because the types of data that most people want to see are seasonal rainfall to date, and normal rainfall for a month. With two seasons of rainfall data nearly complete at this writing, this means that there are only two sample points to calculate an average from. That is not enough, especially since the 2000-2001 season was under average, and the 2001-2002 season was probably the lowest rainfall totals that we'll see in decades. Some areas in California (Palm Springs) have seen all-time low amounts of precipitation for the 2001-2002 season. In another year or so, WeatherCurrents.com will provide normal rainfall to date totals on Temecula's main page and normal rainfall by month on the Climate Page.

For the Murrieta site, which is brand new as of this writing, the normals from the above formula are calculated from only the preceding five days and should be used with caution for the next couple of years.

Until such time as WeatherCurrents can accumulate several years of data in our archive, please treat the normal conditions computed herein as best guesses, and know that they may be a little inaccurate. Time will correct any inaccuracies; every day that passes will make a difference. But we think even at this early stage that they will be close.