PUBLISHED : Sunday, 25 April, 2010, 12:00am
UPDATED : Sunday, 25 April, 2010, 12:00am

The Russian River Valley, in California, is one of Sonoma County's coolest wine-growing regions. While day- time temperatures hover at about 15 degrees Celsius, at night it can drop to as low as five degrees and, up until recently, snow could be seen on the nearby Mayacamas Mountains, the range that divides Sonoma from inland Napa County. Although daytime temperatures will soon warm up, the nights will remain dramatically cooler, sometimes with a difference of as much as 20 degrees. This phenomenon is known as 'diurnal temperature variation' and is key to the success of many high-altitude wine regions. Such dramatic temperature swings result in grapes with high ripeness due to long, sunny days, yet with surprisingly fresh acidity, because the cool nights preserve the fruit's natural acidic balance.

White Oak chardonnay 2007, Russian River Valley, California

White Oak is based in Alexander Valley, near the quaint town of Healdsburg, but it sources fruit from sites within Sonoma County. It's easy to be seduced by the chardonnay's ripe, tropical mango and citrus flavours. Oak handling is well integrated, contributing nutty and vanilla accents. This is a buxom chardonnay but it gracefully holds up in the glass, even two hours after being opened, delivering aroma, flavour and length. Serve with roasted chicken or other rich and savoury white meats.

Available for HK$284 at California Grapes International (tel: 9631 1951)

Buehler Vineyards chardonnay 2008, Russian River Valley

Ripe yellow apple with lemon-tea accents. This is a lean, minerally wine with balanced acidity and a clean finish, highly suitable for shellfish.

Available for HK$166 at Golden Gate Wine (tel: 2891 8121)

Francis Ford Coppola Director's Cut chardonnay 2007, Russian River Valley

Subtle ripe apple with hints of spice followed by light butter and a toasty oak finish. This is a versatile 'all-rounder' that will play with dishes as varied as xiao long bao, buttered sole and drunken chicken.

Available for HK$219 at Golden Gate Wine

Debra Meiburg is a master of wine