Yesterday was a dark and stormy day here on the hilltop. The weather report says that we got 0.42 inches of rain, which in an area that averages 10 inches per year, that’s a healthy rain day. Hidden Meadows (of which we are technically a part of even though it is not an incorporated village) receives between approximately 5.6 and 13.6 inches of rainfall per year , with sources varying somewhat. One source reports an annual average of about 10 inches. San Diego County coastal areas average roughly 10 inches per year, while inland mountain areas can receive more than 33 inches annually. I guess that makes us more like the coast than the vast ranch lands to the east. I’m not sure I would have guessed that based on the fact that those areas always seem hotter…but then that also encompasses some pretty large areas of more alpine forests as well as the more obvious deserts like the Mojave and Anza Borrego.
That makes us somewhat drier than the rest of Southern California and the state overall. Downtown Los Angeles averages about 11.90 inches per year, whereas California as a whole averages 21.44 inches annually. That means that our hilltop falls on the lower end of Southern California’s precipitation range, typical of inland valleys in San Diego County that don’t benefit from mountain orographic effects. The orographic effect is when mountains force air to rise, causing increased precipitation on the windward side (the side facing the wind) and creating drier conditions on the leeward side (the downwind side). In Southern California, this effect is very pronounced. The windward side, the coastal mountains facing Pacific storms, can receive 30-40+ inches of rain annually. But the leeward side, the inland valleys and deserts in the “rain shadow” receive much less…sometimes under 10 inches. This is why places like Hidden Meadows (in an inland valley) are much drier than the nearby mountains, and why California’s inland deserts are so arid despite being relatively close to the ocean. The mountains essentially “wring out” the moisture from air masses before they reach inland areas. The Sierra Nevada mountain range creates one of the most dramatic examples of this effect in North America, with lush western slopes and the arid Great Basin desert to the east.
That’s probably why is all somewhat confusing to me because I can see the Pacific Ocean and I can see the mountain ranges to the east. I know we are warmer than the coast and also drier than the coast, since I can always see the maritime layer that tends to envelope the coastal areas especially during the summer. But I always think of it being even warmer and drier to the east (due to the desert), but the truth is that that only holds until you get to the next mountain ranges that force the next chapter of the orographic effect and wrings more moisture out of the air as the combination of elevation and wind drives the air higher and cooler. That is all very consistent with my gardening observations of this hilltop. It is a fascinating blend of tropical and arid. Cacti and succulents do particularly well here, but the flowering trees and bushes like bougainvillea and Crepe Myrtle also do well here. You can drive by what looks like an Arizona zerascape front yard and then turn a corner and feel like you are on a small hidden road in Bermuda, with lovely flowered bushes all around you.
Hidden Meadows is significantly drier than the U.S. average when it comes to rainfall. The United States (excluding Hawaii and Alaska) averages 30.21 inches of precipitation annually. This means Hidden Meadows receives roughly one-third to one-half of the national average rainfall. Hidden Meadows’ semi-arid climate is characteristic of the region’s Mediterranean climate pattern. That’s probably why its such an appealing place to retire for people like us. Who doesn’t like a good Mediterranean climate pattern, right?
According to the USDA Hardiness Zone Map, Hidden Meadows is in zones 9b (25°F to 30°F) and 10a (30°F to 35°F) . This represents mild winter conditions ideal for year-round gardening. The growing season in zone 9/10 typically lasts from late February to early December, extending through the end of the year if days are mostly sunny. There are mild winters with rare frosts and hot, dry summers, allowing for nearly year-round planting. I don’t grow vegetables, but in terms of ornamental Plants, trees and shrubs, we have everything from showy flowers such as amaryllis, iris, hibiscus, and roses that thrive in full sun (roses bloom here year-round) as well as shade-tolerant plants like begonias and peonies and Lots of native wildflowers including columbine, yarrow, coneflowers, California poppies, and black-eyed Susans. Heat-loving perennial flowers and ornamental grasses do well. The hills are covered with indigenous live oaks and manzanita trees with fruit trees (citrus, avocado, stone fruits) all doing well while even desert trees like the Palo verdes also thrive. Due to Hidden Meadows’ low annual rainfall, drought-tolerant plants survive easily, but efficient irrigation is essential for almost everything else. Succulents including prickly pear cacti, all kinds of aloes and agaves all abound due to the arid conditions. Mediterranean herbs like rosemary, lavender, and sage are particularly well-suited to the climate and adorn the boundary areas of my gardens both front and back.
San Diego weather is widely considered one of the best climates in the world for human comfort. On average, 344 days a year are warmer than 60°F on this hilltop, but only 25 days exceed 80°F. There are on average zero days below 32°F in San Diego, while the national average is 88 days . San Diego also averages 146 sunny days and 117 partly cloudy days per year . The national average for mostly sunny days is 213 while San Diego’s is 267, and thus, significantly more sunshine than most of the country. San Diego sees 21 days with precipitation per year while the rest of the country sees about 110 . Our coastal proximity provides moisture without oppressive humidity. Unlike humid subtropical climates (think Florida or Houston), San Diego maintains comfortable humidity levels that don’t make the heat feel stifling. The mild temperatures mean less stress on cardiovascular systems, no extreme cold to constrict blood vessels or dangerous heat waves requiring indoor refuge. The combination of sunshine and comfortable temperatures combined with low humidity encourages year-round outdoor exercise and my favorite activity…gardening. Abundant sunshine and lack of harsh winters help many people maintain better mental health year-round. We are less crazy here…or at least should be.
But…we do have a few downsides. We get the Santa Ana winds. These occasional easterly winds bring hot, dry air from inland deserts, creating wildfire danger and uncomfortably hot conditions for a few days, typically in the fall. We also get a bit of the marine layer, when the coastal areas experience morning fog and overcast conditions, especially in May and June (“May Gray” and “June Gloom”). Some people miss the distinct seasonal changes found in other climates with no fall foliage, snow, or dramatic spring blooms (though we do get the nearby February Superbloom). That is one of the reasons why when we do have stormy weather like yesterday, we all sort of smile and relish it…it gives us something to remind us of how good we have it most of the time.