For a white wine nothing says summer like Sauvignon Blanc. It's lighter-bodied than most Chardonnays and has more acid meaning it's crisp and refreshing. From Sonoma County you've got Geyser Peak and Kenwood on the less expensive end of the spectrum. Then there's Hanna Winery with what I'd call the gold standard of Sauvignon Blancs. But there are dozens of top-notch SBs from the Russian River Valley and parts of Dry Creek Valley.
Want something a little different? Look for a Marsanne or other Rhone-style white blend. Or even wilder, try to find a Grenache Blanc.
In a red wine a good quality one on the lighter side is the way to go. How do you know if you're getting an easy drinking, lighter red wine? Look for grape varieties such as Pinot Noir, Grenache, Malbec, and Cabernet Franc. Just as important look at alcohol levels. Once you hit the mid-fourteens on most of these they are getting out of the range of what I'd call "light" or a "warm weather" wine.
|Alexander Valley Vineyards and|
Valley of the Moon Winery
make excellent Rosé based on Sangiovese
Image from avwine.com
|But there's nothing wrong with going this way|
Image from sierranevada.com