Baja California Peninsula Geography & Climate

Baja California is one of the longest peninsulas in the world — about 1,250 kilometres from the United States border to its southern cape, and rarely more than 150 wide.

A torn-off piece of Mexico

The peninsula sits on the Pacific plate rather than the North American one, and it is moving north-west with it. The Gulf of California is a young ocean basin opening along the same fault system as the San Andreas, and the peninsula was attached to the mainland until a few million years ago. It is still separating, a few centimetres a year.

Mountains and desert

A spine of sierras runs the length, reaching about 3,000 metres at the Picacho del Diablo in the north, where there are pines and occasional snow. Everything else is desert — the Sonoran in the north, with the strange Valle de los Cirios where boojum trees grow like inverted carrots and exist nowhere else on earth.

Two very different seas

The Pacific side is cold, foggy and rich, with upwelling that supports the whales and the fishery, and the lagoons where the greys calve. The Gulf side is warm, clear and enclosed, with high evaporation, strong tides at its head and an extraordinary concentration of marine life — around nine hundred fish species and a third of the world’s marine mammal species.

The Colorado that no longer arrives

At the head of the Gulf, the Colorado River once built a vast delta and pushed a tidal bore up its channels. Upstream damming and abstraction in the United States now take almost the entire flow, and the river usually reaches the sea only as a trickle or not at all. The delta has largely dried, its wetlands shrunk by most of their original extent, and the vaquita porpoise that lives in those waters is the most endangered marine mammal on earth.

Water

Rainfall is under 200 millimetres almost everywhere and near zero in places. There are no permanent rivers of consequence.

Baja is desert from end to end, but the two coasts behave so differently that they need describing separately.

The Pacific side

Cold water upwelling keeps this coast remarkably cool — often 18 to 24°C even in summer — and produces persistent morning fog that sustains lichen and succulents in country that gets almost no rain. Ensenada and the northern coast have a Mediterranean pattern with what little rain there is falling in winter.

The Gulf side

Much hotter. The enclosed sea heats up, and summer temperatures along the Gulf coast and in the southern interior regularly exceed 38°C with high humidity from June to September. Winter, by contrast, is close to perfect: 24 to 28°C, dry and clear.

Rain, or its absence

Most of the peninsula receives under 200 millimetres a year, and the central desert can go years between meaningful falls. When rain does come it arrives all at once, and dry arroyos become dangerous within minutes — flash flooding is the most common cause of road closures and deaths here.

Hurricanes

Chubascos track up from the south between June and November, peaking in September. Baja California Sur is hit periodically and the damage can be severe; Odile in 2014 wrecked much of Los Cabos.

Fog as rainfall

On the Pacific coast the fog does the work that rain does elsewhere. Moisture condenses on plants and drips to the ground, and whole communities of lichen, succulents and the boojum depend on it rather than on measurable precipitation. It also means the Pacific side can be grey and cold at nine in the morning and brilliantly clear by noon, which catches out anyone planning a beach day by the forecast.

The desert in bloom

After a wet winter the desert flowers in February and March, which is unpredictable and worth catching.