Port anD the Douro 57200mm at Fontes in the west of the region to 50.6mm at Barca d’Alva in the east. But
weather patterns are unpredictable and vineyard yields are easily diminished by relatively
cool, wet Atlantic weather at the time of flowering in late May or early June. A westerly
airstream prevails for most of the year, but the wind occasionally veers round from the
east bringing scalding weather conditions from central Spain during the summer months
and dry, biting winds in the winter. This gives rise to the rhyme readily trotted out by
locals that ‘nem bom vento, nem bom casamento vem de Espanha’ – neither a good wind nor
a good marriage comes from Spain!
As rainfall declines inland, so temperatures increase. The annual average daytime temperature
in Oporto is 14.4°C, rising to 15.5°C at Régua, 16.2°C at Pinhão and 16.5°C at Pocinho. The
highest annual average temperatures are found along the river and fall to as low as 11.8°C on
the higher margins of the region, but these averages obscure the extremes that increase markedly
towards the Spanish border. During the winter months the thermometer frequently falls below
freezing on the northern planalto, the area known by the locals as the Terra Fria (Cold Land).
In summer it has been known to rise to an unbearable 50°C in the deep valleys of the upper
Douro; the Terra Quente (Hot Land). Since the river was dammed in the 1970s (see page 45),
a blanket of freezing fog often hangs over the Douro when atmospheric conditions are stable
during the winter. Late spring frosts are not uncommon at higher altitudes, damaging young
shoots in the vineyard and sometimes wiping out the potential crop.
Given the contorted terrain, there is also considerable variation in the microclimate
- not just within a single vineyard but within a single terrace, right down to micro
variations within the vine canopy. Despite an increase in research into the microclimatic
ramifications arising from differing methods of cultivation, vine spacing and trellising,
most growers still rely on empirical knowledge of their own vineyards. Many larger
properties embrace a number of different exposures and can span an altitude range of 300
metres or more. For example, at Quinta de la Rosa, which ranges from 90 to 260 metres
above sea level, the difference in temperature between the top and bottom of the vineyard
can be as much as 4°C. As a result, ripening and therefore picking dates can vary by as
much three weeks within one property.
The climate of northern Portugal also has a bearing on the ageing of Port, and this is
considered in Chapter 4.
the suB-regions oF the Douro
The Douro divides naturally into three sub-regions, each of which has its own distinct
mesoclimate and therefore tends to produce a different style and character of Port.
The smallest of the three sub-regions in overall area is the Baixo Corgo (below the
Corgo). This is the most westerly and therefore most accessible part of the Douro centred
on the city of Régua where the Port trade first took hold (see page 10). Covering a total
area of 45,000 hectares, it is still the most intensively planted part of the Douro valley with
a total of 14,100 hectares, representing 31.3 per cent under vine. With 13,850 registered