(Wine-Searcher) - Rain was a major factor in the harvests on both sides of the Andes.

Chile

Chile has had a pretty wild ride this year, marked by floods and volcanic eruptions.

The resulting wines will be mixed but the warm season looks promising for Mediterranean varieties.

Starting in the north of the country, a hot and very dry growing season pushed harvest times forward by a couple weeks. "We have had an early harvest this year with big bunches and lots of fruit," said Emily Faulconer, winemaker at Viñedos Alcohuaz in Elqui. "The green harvest was very important this year" to restrict yields and allow fruit to ripen.

For all the dry conditions during the majority of the year, Mother Nature certainly made up for it on March 25; a freak rainfall dumped the equivalent of seven years' worth of the region's rainfall in less than 12 hours, reaching parts of the Atacama desert that hadn't seen rain for centuries. Treacherous mud avalanches were fatal, although only affected minor vineyard plantations in Chanaral. In Limari, where harvest was halted for a few days until conditions dried up, the rain was a blessing in disguise for an otherwise parched region.

Further down the coast, in Casablanca, the hot year fanned a bush fire between the wine region and port city Valparaiso but fortunately vineyards were left unscathed. "2015 was a special harvest because we had a warm summer and autumn, with lower rainfall than the previous year," commented Felipe Garcia from Garcia-Schwaderer. "We had a normal yield, but an early increase of sugar concentration. For that reason we picked some fruit without full ripening, [to maintain acidity]."

It was a battle for acidity across the Central Valley with a hotter harvest in most places, although rainfall mid-harvest in March proved a relief for some producers. "This year is very unusual because at the end of spring it was very hot, which means normally we have a lot of sugar," said Marcelo Retamal from De Martino wines. "Then we had a good rainfall – huge for the area, and this meant the sugar decreased leaving us with very well-balanced alcohol and acidity. The acidity is lower than average in Maipo but there is no greenness in the wine. I don't know if it is an outstanding vintage, but we need to wait; is very unusual. I wasn't happy at first but after the rain it was more promising."

Even in the cooler growing regions further south – in Itata and Bio Bio – the summer heats spiked in the mid-30s, which was unusually hot for the region. "Fortunately the older vines are more balanced and can cope with this very hot year, in which we didn't have the usual rains," comments Enzo Pandolfi, who produces Chardonnay at his family winery Pandolfi Price in Itata.

Fortunately for Chile, the Calbuco volcano eruption in the far south (three eruptions at time of print) appears to have had minimal impact on the small growing regions nearby.

Argentina

Argentina received the tail-end of Chile's odd climatic year. In the south, the Patagonian region of Chubut had to pick earlier than planned in order to avoid ash fall from Chile's volcanic explosion damaging the crops. "Normally in the region, Merlot is harvested between May 2-5, but we had to pick it early because of the bad predictions of ash settling," said Dario Gonzalez, a consultant in the region.

In Mendoza, the heartland of Argentine wine, the harvest was unusually wet and warm. Many producers, who are not used to dealing with humid conditions in its normally dry climate, lost large quantities of fruit to adverse conditions. "This harvest was a very strange one," commented Leo Erazu, winemaker for Altos Las Hormigas. "It started really warm for two months, and then the constant rainy periods affected some areas very badly, and strong hailstorms damaged a lot of hectares. Rot attacks were very common from March onwards; downy mildew attacks were widespread in all the Pedriel and Agrelo areas. The hail badly affected some regions such as El Peral in Tupungato, some vineyards lost up to the 50 percent of the yield … Harvest time was very important this year. Because of the human scale of our project we still managed to taste every block of grapes, and harvested almost everything before the rain came."

The challenge this year was on getting the timing right; dodging the rains and coping with the early harvest. "The spring buds arrived 20 days earlier than a normal year," said winemaker Matias Michelini, winemaker for Passionate Wines, Zorzal and Sophenia in the Uco Valley, where he is always one of the first to harvest. "It has been one of the shortest harvests I remember. The year has been hot and with a greater quantity of rain than expected for Mendoza, you had to be really focused on deciding the harvest dates."