Bonny Doon Rainfall Gauge

Highlights of the Current Season - July 1, 2004 - June 30, 2005

          September was quite pleasant, and then turned cool and then winter like on the 18th, with night temperatures in the 40's. Early light rain fell on the 19th. Indian summer followed, with pleasant warm days and cool nights into mid-October. A shift to the rainy season appeared on the weekend of October 16th, with cooler temperatures. A bit over half an inch fell overnight, and another inch fell during the day, starting the rainy season on the 17th. The 19th brought heavy rain onto the coast. Thunderstorms rolled through the early morning hours of the 20th. More thunder and lightning and moderate rain fell on the 26th.

          Winter arrived with the first frost on November 4 and a trace of cold rain. A series of storms brought soaking rain to the mountain on Nov. 10th and 11th. It was pleasant and seasonable until the 26th, when a fast moving storm brought nearly 2 inches of cold rain overnight. Another fast moving storm dropped over 3 inches of windy rain on the 7th of December, followed by steady heavy rain on the 8th. On the 27th, a stationary system moved in and stalled over California, bringing nearly 10 inches of rain to our mountain in a couple of days. And the new year came in with cold and wet conditions. A very powerful storm made landfall in the early morning hours of the 7th, with high winds and substantial rain. A nice January thaw lasted until the 26th, when rain and cold air moved in from Alaska. A quick and windy storm blew through on the night of the 27th/28th. Early February was mild and sunny, with a brief soaking rain on the 7th. More wet weather arrived during Valentines day and on during the following week. And the end of February brought more cool conditions and light rain.

          March came in wet and cool with a quick downpour of cold rain on the 1st. The second week brought record high temperatures and the third week was spring-like, with sunny and warm days and cool nights. A very strong Pacific storm made landfall on the 18th, bringing heavy rain and cool temperatures to the mountains, followed by a series of fast moving storms the next week. Spring seemed to arrive at the end of March, but cool and wet weather returned in early April. And the unsettled weather continued into late April. Early May was unsettled and damp. May 8th was winter-like, wet and cold. Spring finally arrived on May 14, with warm temperatures, light breezes and clear skies. A quick cold storm came ashore on May 18th, followed by warmer and drier weather on the 20th. June was warm and clear, except for the 7th and 8th, which turned cold and blustery, with a little rain overnight. Warm weather quickly returned, followed by another rare June rain event on the 16th and 17th. Summer temperatures finally arrived in late June, with fog at the beach.

The Rain Guage

          I keep these unofficial readings as a personal interest. I have seen our reading exceed other gauges that are located at lower elevations nearby, so I figured this might be of interest to others. For rainfall amounts up to 5 inches, I use a retail rain gauge. When amounts overnight are higher than 5 inches, I use, as a backup, a simple vertical wall bucket capable of holding up to 14 inches. I have to use the bucket at least a few times every winter. In years past, I was distrustful about the unusually high rainfall readings, changing gauges and trying various methods and locations to improve accuracy. However, after much experimentation, and then checking with our neighbors, I think we are simply in a micro-climate with more rain than other places. This is the Santa Cruz Mountains, after all. As the Weather Service says, we are in an "Orographically Favored Location." I think that means we get soggy when others simply get wet.

          There is one official California Department of Water Resources weather monitoring site located nearby, at a slightly higher elevation. They match my readings here at 2200' fairly well. You can compare for yourself, at Ben Lomond Mountain (2630', three miles up the road from here). Their measured rainfall tends to be slightly less, but the temperature tracks pretty close to our location.

          There are also a couple of other nearby, lower elevation locations where rainfall is measured. One long-time measurement created by Ted Cantrall is here and another, run by the folks at Anometal.com can be found here.

          As with most places in this region, we are in a "micro-climate". Ours happens to be very wet during the rainy season, due to our location, elevation and southern exposure to incoming storms. During large storms, average winds of 40 to 60 mph are typical here. In December of 1995, we had winds approaching 100 mph, and during February, 1998, peak winds approached 85 mph. The season is officially measured from July 1 to June 30, although rain usually only falls between September and May, a typical "dry and wet" seasonal pattern. Snow does fall here, but it is usually not more than a few inches at a time. The temperature range is not too extreme, and only falls below 25 degrees a few weeks every winter. 1991 was the exception, with lows in the teens for over a week. The winters of 1973, 1975, 1982, 1995, 1998, 2001 and 2002 brought significant snowfall.