View of the Rainbow Gap from Wilson Creek. The gap is the one on the left. 


The Rainbow Gap: Temecula Valley Breathes 


Yes, good wine regions breathe. And, so do vines. Great wine regions flourish through wind flow. And the best part? It’s all through nature’s impeccable design. 


The Importance of Mountain Gaps For Grape Growing

Mountains are typically needed to create a barrier from the ocean influence. No barrier to the ocean influence results in a lot of air flow and high winds – weather that’s too harsh for grapes.  

However, if there is too much of a mountain barrier, there is not enough flow from the coast, as the air currents are blocked off. 


So, a mountain gap is critical – it acts like an opening and operates like a windpipe, drawing air in and out between the ocean and the valley.

The Rainbow Gap in Temecula

The mountain gap between Temecula and the ocean is called the “Rainbow Gap”. In Temecula Valley, we are nestled between two mountain ranges. West of Temecula, between San Onofre Beach and Camp Pendleton, there’s the Rainbow Gap. The mountains east of Temecula, Mt. San Jacinto, separate Temecula Valley from the heat of Palm Springs. 


How Does The Rainbow Gap Work?

In the morning hours, the wind in Temecula is relatively still, sometimes flowing slightly west. Then around 10 or 11 a.m., Palm Springs heats up, and the rising hot air creates a vacuum that pulls in the cool ocean air from over 30 miles away. That vacuum pulls the ocean air through the Rainbow Gap and it settles into our valley. Then, in the evening, when the air in the east mountains cools down, the air gets heavier and gently flows downhill/westward back into the valley, cooling Temecula Valley at night. 


How The Rainbow Gap Creates Ideal Wine Growing Conditions 

The valley inhales the ocean air in the late morning through the Rainbow Gap, then at night, the air gently flows back down into the valley. This coolness at night allows the grapes to recoup and rest a bit from their hard work of photosynthesis during the day. 


Some of the most famous wine regions have a similar “breathing” process, including Napa Valley, Paso Robles, Bordeaux and even The Rhone Valley in France.


This breathing creates a necessary diurnal shift that grapes need. Grapes like hot days and cool nights with low humidity. The shift from the hottest time to the coolest time is called the diurnal shift. All good wine regions have a big diurnal shift. Temecula Valley can often shift 40-50%, which could mean 98 degrees to 50 degrees on the same day!


While the valley breathes, the vines and soil get love, too. Vines inhale CO2 all night long and exhale oxygen all day long. The soil does the opposite—it inhales oxygen all day and exhales CO2 all night. They enjoy a symbiotic relationship by feeding each other. For the vines, the CO2 is heavier and falls to the ground and the soil ‘inhales’ it.”

With ideal growing conditions, you can say that Temecula Valley is made for quality wine grapes and great tasting wine.


So, when you visit Temecula Valley again and feel the breeze that flows from the ocean to the west, you can be thankful for the Rainbow Gap. And, next time you go wine tasting, ask about how the area breathes and the diurnal shift to find out exactly how nature’s perfect design brings great wine to your taste buds. 




Post by: Mick Wilson  

Mick Wilson is a Certified Sommelier with the Court of Master Sommeliers as well as a Certified Specialist of Wine with the Society of Wine Educators.  He also teaches various subjects at the Wilson Creek Wine Academy.

Learn more about Wilson Creek Winemaking.