Weather in the Channel Islands

As with the ocean currents, the air currents in the Channel region are also influenced by Point Conception and by distant forces out over the Pacific. The westernmost tip of the Channel region is Point Conception, with the Santa Ynez Mountains as a backdrop as they march to the sea. This protective arm of mountains, from Point Conception inland behind Ventura, forms a protective mountainous barrier that shelters the region from harsher northerly weather patterns, and buffered the area from the direct force of arctic storms moving down from Alaska. It is here Southern California technically begins, and the Mediterranean climate begins with its milder winters.


Island Weather

Each Channel Island has its own distinct weather pattern, and sailors learn to recognize the signs of forthcoming weather carefully. To sail out of Santa Barbara harbor with one single weather report will not necessarily mean consistent conditions – in fact it rarely ever will. The weather on the Channel is a powerful force –and notably – it is by looking up over the Santa Ynez Mountains that gives sailors the most accurate visual cue, not looking out over the Pacific.

Each island’s weather is directly impacted on by its relation to Point Conception. The northern Channel Islands are not equally protected by Point Conception – in fact San Miguel lies so far to the west it receives very little protection at all, while Santa Cruz and Anacapa Islands are situated well into the protective east-west curvature of the coast.

San Miguel has the harshest, windiest weather that, combined with severe over grazing, has worn down the island to low hills ( tallest peak is 831 feet ) and constantly shifting sand dunes. It has experienced many long periods of severe drought.

Santa Rosa is less windy than San Miguel, has a mountain peak of 1.589 feet, strong prevailing winds are arrive from the northwest, and has been successfully used for ranching operations for generations ( now ended to turn the island into a national park site ).

Santa Cruz is well protected from the harsher northwesterly winds, but has actually been blanketed in snow during the winter months ! Annual rainfall is comparable to the mainland at 20 inches, but there have been great variations – from 6.5" to 60". The island is large enough to have a multiple of microclimates – as on the mainland – the coast can be shrouded in fog while the inland island valley is drenched by sun. The inland valley and canyons can exceed 100 degrees Fahrenheit in summer, and frost can effect the interior areas. The coastal shorelines have more moderate temperatures – usually not over 85 or under 35 degrees. The pleasant weather and availability of fresh water supports a diversity of wildlife on Santa Cruz.

Anacapa is the furthest inland of the four northern Channel Islands. Its rainfall is much lower than its neighbor Santa Cruz rarely exceeding 11 inches a year. The western island creates a rain shadow for he middle and eastern island, and their rainfall is significantly less, down to 6 inches a year. There is no reliable source of fresh water on Anacapa. The reason for the drier climate and lack of fresh water is tied not only to the weather, but also to the lack of forest vegetation and mountain peaks on the island where moisture is trapped and rainfall created in a natural precipitation process. The island relies on moisture from fog as well as the scant rainfall for precipitation.

Santa Barbara Islands is the smallest Channel Island and is situated between the northern and southern island groups. The island is temperate – rarely exceeding 90 degrees in the summer as it is cooled by northwesterly winds.

San Nicolas Island has enough precipitation to create a few natural springs, as were relied on by the Native Americans, including the lone Woman of San Nicolas. But the annual rainfall is only around 8 inches. As one of the two islands in the extreme east of the archipelago, it has harsher winters than the other islands as it is more exposed to the rougher weather that comes down off the north Pacific. The winds are relatively constant.

Santa Catalina is close enough to the mainland to reflect a similar weather pattern to the Los Angeles area, but it is buffeted by harsher winter winds off the Pacific. The variations in island topography provide for microclimates, much like on Santa Cruz Island. The annual rainfall at 12 inches in lower than Santa Cruz Island, and reflects a more arid, northern Mexican weather influence than a North Pacific influence. The island is usually visible from the mainland, but is at times shrouded by fog. And fortunately for Catalina islanders, the island is not able to remain fairly clear of the pollution from the Los Angeles basin unless the inland Santa Ana winds blow off across the desert and push the basin’s air out to sea.

San Clemente Island is the southernmost of the Channel Islands, and reflects a closer proximity to the weather patterns common to Baja California, its close neighbor. The most arid of the islands, it is remarkable that it does have enough rainfall to maintain year round springs. It also disappears into coastal fog banks at times, providing welcomed relief from its warm climate.


Weather Events

Through out Channel Island recorded history there have been many unusual weather events. The region is plagued be severe droughts in a cyclical pattern. These droughts have lead to entire deforestation of San Miguel Island by sheep searching for survival in a year with no rain; birds have dropped en mass from the skies, and cattle died in the fields, in Santa Barbara when temperatures once soared to 133 degrees under Simoon conditions ( an Arabian desert term ) when hot airs swept in from the north. Annually the Santa Ana winds blow across the region – coming hot off the deserts in the east, bringing scorching dry weather to the coastal areas. 1988 saw the most rain fall for Santa Barbara County in fifty years.

Fog

The Channel Islands – and Southern California coast - are often enshrouded in fog, called the marine layer. This is caused by warm air from interior valleys meeting the cooler air of the ocean, and then the warm air pulls moisture up out of the ocean to cause the fog. This condensation of water into the air is most prevalent when the contrast between the land air and ocean air temperatures is greatest. For example, in the summer months when the North Pacific- Oregonian – ocean current brings down cold water from Alaska, is when the inland valleys are the direst and hottest. That hot air flows out over the colder ocean water, and the water condensation that occurs is the source of the fog. Likewise, in winter, when the land air is cooler, and the ocean air is warmer due to the Davidson Current coming up from Mexico’s tropical region and into the Channel, the fog does not occur as often.

Southeasters

Southeasters are one of the most dangerous weather patterns in the Channel, and were written about in Henry Dana’s famous book, Two Years Before the Mast in the early 1800s, before the gold rush. This is an event where the wind shifts suddenly, and then rips so forcefully through the Channel that it can tear masts off boats. The wind starts by coming down into the Channel from the Northwest, blowing to the Southeast. Then it rotates around and when it comes in from due West, there is a silent lull that sailors know means trouble ahead. Then it suddenly shifts all the way around and blows from the Southeast to the Northwest, having reversed itself a complete 180 degrees. As it whips around, the sudden powerful gusts can grab a ship's sails and tear the sails and mast right out of the deck. To compensate, when the winds coming from the Northwest suddenly drop, the sailors know to quickly lower all their sails and tie everything down tightly. Then when the wind whips around from the opposite direction, the masts have a better chance of staying intact since there is not the surface of a sail to catch the wind and tear it from the deck.