March in Napa Valley falls late in the rainy season and at the very start of the growing season. Afternoons usually reach the mid 60s, and wild mustard still paints the vineyards yellow between the bare vines. The month brings about 3 to 3.5 inches of rain in a typical year, less than January or February, though strong atmospheric rivers can still arrive. For visitors, March is a quiet shoulder season. The hills are green and the temperatures mild, hotel rates are often lower and the valley feels calmer than during harvest.
What Are March Temperatures in Napa Valley?
In downtown Napa, March afternoons average in the mid 60s, and nights fall to around 42°F. Calistoga, at the north end of the valley, is a few degrees warmer in the afternoon and often a few degrees colder at night. It sits farther from the cooling influence of San Pablo Bay, and cold air drains off the surrounding mountains onto its valley floor after dark.
Frost is still possible on clear, calm mornings, especially on the valley floor. Vineyard managers watch the overnight forecast closely, because a frost after the vines start growing can damage the season's crop before it begins. On cold nights, you may hear large frost fans running before dawn, mixing warmer air down from above to protect the young shoots.
By late March, the valley starts to warm noticeably. Afternoons in the upper 60s become common, and a warm spell between storms can push highs into the 70s. Those days hint at the season ahead and make late March one of the most pleasant times to be outdoors in wine country.
March sits between two very different months. February is usually wetter and a few degrees cooler, with more frosty mornings and shorter days. April is drier and warmer, with afternoons that often reach the low 70s, but the mustard is mostly gone by then and the vines are leafing out. March offers a little of both, with winter's green landscape and the first taste of spring warmth.
Mustard Season and Spring Bloom
Napa's mustard season runs from about January into March, when wild mustard blooms in the rows between the dormant vines. Bright yellow flowers against bare, dark vines and green hills make one of the valley's most photographed scenes. Growers often plant or leave the mustard as a cover crop. It protects the soil from erosion during the rainy season and adds nutrients when it is turned under, and several wineries hold mustard-themed events while it blooms.
By late March the mustard starts to fade. Many vineyard crews then mow or plow the cover crop under before the vines start growing. Bud break, when the dormant vines push out their first green shoots, usually comes in March. Early grapes such as Chardonnay tend to wake up first, and Cabernet Sauvignon often follows later in March or early April. A warm winter can bring bud break in late February, while a cool one can delay it into April.
Wildflowers spread across the hills at the same time. Poppies, lupine and other spring flowers begin to bloom on sunny slopes, especially after a wet winter. A hike in the hills above the valley in late March can be as colorful as the vineyards below.
Rain in March
March rain in Napa usually totals around 3 to 3.5 inches, spread over 8 to 10 rainy days. It tends to come in bursts, with a storm lasting a day or two followed by several clear days. Between storms, March can be beautiful, with clear skies, mild afternoons and air washed clean by the rain. On those days, the green hills and yellow vineyards look especially vivid.
Some years bring much more rain than that. A strong atmospheric river can drop several inches in a single storm, and the Napa River, which runs high through the wet season, can rise quickly. Most March storms are smaller, but it is worth checking the forecast before a trip and watching for flood alerts if a big storm is on the way.
Visiting Napa in March
March is one of the best shoulder-season months to visit Napa. Hotels and restaurants are less crowded than at harvest, rates are often lower and tasting rooms feel relaxed. Between storms, the weather is good for being outside. Hiking at Bothe-Napa Valley State Park, cycling on the valley floor and sitting on a winery patio are all pleasant when the sun is out.
Pack a rain jacket and layers, because March weather can change quickly. A sunny 68°F afternoon can turn into a rainy 55°F evening, and early mornings are often cold enough for a warm jacket. Shoes that can handle a muddy path are useful too, since vineyard edges and trails stay soft after rain.
Hot-air balloon flights over the valley run in many months, and March can be a lovely time to go up. Balloons launch around sunrise, when the air is calmest, and the view of green hills and yellow vineyards can be spectacular. Rain, low clouds or wind can cancel a flight, though, so keep your schedule flexible and expect the operator to make the call early that morning.
That changing weather is part of the appeal, because in March you see the valley at its greenest and most natural, before the summer crowds and heat. A little flexibility with your plans is the only price for one of the prettiest times of year in wine country.
