Posted January 30, 2008, 1:19 PM.

The normal-to-date reading is calculated from actual past rainfall, from the years where we have it available.

For instance, Temecula, the oldest WeatherCurrents site, draws actual rainfall totals from 2001 through 2007, for a total of six seasons. On January 30th, the average of these six seasons was 6.18", and was going forward in spurts depending on the day.

Only complete seasons of rainfall are considered.

Other sites displaying normal-to-date rainfall include Hemet, Murrieta and Fallbrook, and are displaying somewhat different values. As an example, Murrieta's normal-to-date was calculated to be 9.21" on January 30th. Hemet's was 8.01", and Fallbrook was at 10.48". Hemet has four seasons of rainfall available to average, Murrieta and Fallbrook only three.

The averages for Murrieta, Fallbrook and Hemet are skewed by a near-record rain year in 2004-2005.

As a result, the normal-to-date rainfall values for Murrieta, Fallbrook and Hemet should be considered to be less accurate than Temecula, and Temecula should perhaps not be considered to be too accurate either, although it is closer to the true average.

We currently think the values for all of the sites are too high

More years of data will make all of the values accurate.

We generally make the normal-to-date rainfall feature available after a weather site has three complete seasons of data.

After July 1st this year, normal-to-date rainfall will also be displayed for Menifee Valley and Lake Elsinore.