Of all aspects of viticulture, the weather is probably the single most unpredictable factor involved in the wine-making equation. Microclimates can play a huge part in determining what regions will or will not produce good grapes for fermentation, while a wide variety of issues, from sunlight and temperature to wind and rainfall can have a huge impact on determining whether the wines of a particular region end up being a vintage year or result in a more pedestrian wine. Here we explore the science of wine and weather, before looking at how fluctuating weather patterns across history have changed the story of viticulture over a period of thousands of years.
Wine and Weather: The Science
The science of weather and wine is highly complex. Warm conditions, for instance, are needed for grapes to flourish anywhere, thus the reason why Iceland, Finland, and Canada are not exactly known for their wines. Cool air running through valleys like Napa in California or along the lower climes of mountains like Table Mountain in South Africa aid the cultivation of the best grapes for viticulture, but if there is too much humidity the grapes will suffer. Equally wind, frost, and dew can all play a part in determining the quality of a harvest. For instance, the sirocco wind which comes in from North Africa sometimes reaches France and afflicts the harvest there, resulting in a poorer vintage.
Similarly, the Zonda winds of Argentina can have a deleterious impact on grapes grown in much of the country. As such weather is the most important determining factor when it comes to how high the quality of a wine produced in a given year is. As an indication of this, the Romans prized the Opimian wine which was bottled in 121 BC for decades afterward, such as the coalescence of factors that combined, including a particularly hot summer, to produce the finest of Roman wines that year. Consequently, the climactic conditions in which an individual grape harvest is produced are absolutely vital in determining the quality of the wine. 
Wine and the End of the Pleistocene Period
Perhaps no greater indication of the centrality of weather to wine production is evident than from the fact that viticulture did not become possible until the end of the Pleistocene period. This was the last major Ice Age and it was not until it gradually receded from about 10,000 BC onwards that Homo sapiens were able to begin cultivating Vitis vinifera in earnest in places like China, Georgia, and Azerbaijan from 8,000 BC or so onwards.
And this wasn’t simply because human beings first started drinking alcohol at this time. There is evidence from the Pleistocene period that hunter-gatherers were already producing alcohol at the end of the Ice Age. It is just that effective grape cultivation and with it, wine fermentation was implausible in the colder weather conditions present at that time. With the end of the Pleistocene period and the onset of warmer temperatures viticulture began to flourish in regions such as the Caucasus and the Mediterranean. 
Wine and the Roman Warm Period
As much as viticulture became a staple of many Neolithic, Chalcolithic, and Bronze Age societies between the sixth and second millennia BC, it was really in the first millennium BC that wine culture became central to the civilization of the Mediterranean, particularly amongst the Phoenicians, Greeks, and Romans. Historians used to simply believe this was an issue of the tastes which developed amongst these societies, however recent research has suggested other factors, specifically, the weather, may have also been in play.
The period roughly from the middle of the first millennium BC down to the middle of the first millennium AD saw unusually warm temperatures develop globally, ones which mirrored climactic conditions in the nineteenth century. Studies in the 1990s began referring to this phenomenon as the Roman Warm Period. During it global temperatures were within one or one and a half degrees on average globally of what they are today.
As a consequence, the number of regions across southern Europe and the perimeter of the Mediterranean which became conducive to grape cultivation and viticulture increased significantly. Thus, it appears that not only were the Greeks and Romans more fond of wine in general, but the weather conditions which prevailed during this Roman Warm Period were simply more suitable for the production of greater amounts of wine and wine of better quality. 
Wine and the Late Antique Ice Age
The end of the Roman Warm Period was brought about by a profound crisis that approximated a huge decline in the fortunes of viticulture across Europe. This was the Late Antique Ice Age.Occurring broadly speaking in the fifth and sixth centuries and continuing up residually into the Dark Ages or Early Medieval Period, this saw global temperatures decline precipitously for a period of 150 to 200 years. 
The impact on viticulture may have been difficult to pinpoint. We know that the wine culture of the Roman world went into major decline around this time, but this was broadly owing to the collapse of the Western Roman Empire in the fifth century AD and the emergence of a beer-drinking Germanic culture in regions like Hispania, Gaul, and the Rhineland.
But is it also possible that some of this drift away from a wine-drinking culture in the Late Antique world was owing to failing grape harvests brought about by this miniature Ice Age? This would potentially explain why wine production remained high in regions like the Visigothic Kingdom of Spain down to the early sixth century AD, decades after Roman rule here had collapsed. Here the real decline in viticulture actually occurred from the middle of the sixth century onwards as the Late Antique Ice Age began to bite. 
Wine in the Middle Ages and the Little Ice Age
Our records for much of the Middle Ages which followed the Late Antique Ice Age are admittedly more patchy, but there seems to be clear evidence that by the eighth or ninth centuries weather patterns globally had returned to something approximating the Roman Warm Period. Witness the fact that in the eleventh century there were vineyards growing in southern England and we begin to see a world in which warmer weather patterns were once again pushing the band of areas in which viticulture was possible further to the north. 
But all things in weather and wine are cyclical. Beginning in the thirteenth century a new Little Ice Age commenced which lasted through to the early eighteenth century. At its most extreme in the seventeenth century, it had possibly driven global temperatures down over one and a half or even two degrees on average. This meant that viticulture in southern England or even parts of northern France, Poland, and northern Germany became impractical, where previously it had been possible on a limited scale. Consequently, central and southern France, Spain, Italy, Greece, Hungary, and many parts of the New World which we recognize as intrinsically associated with viticulture today began to emerge as the centers of winemaking in their respective nations. 
Wine and Modern Climate Change
Today we are living in a world where the intrinsic links between wine and weather are becoming ever clearer. As climate change begins to bite hard in the early twenty-first century we are starting to see vineyards in parts of California, Spain, Italy, and southern France which have been intrinsic to their region’s wine industries for centuries begin to suffer. Extremes of heat will damage the harvest in years to come and wildfires will simply destroy vineyards in some places.
Conversely, it is also becoming possible to grow grapes for fermentation in ever more northerly climes. In recent years the number of winemakers in parts of southern England, Denmark and even parts of southern Norway and Sweden has increased. It will be a long time before these challenge the wineries of Burgundy and Bordeaux, but it is all an indication of how changing weather patterns continue to shape the history of viticulture. 
Conclusion: An Ever-Changing Landscape
Thus, from all of this, it should be clear that weather is not just one of the most important factors when it comes to determining the quality of wines produced in a given year, but it is also ever-changing. From year to year wind, heat, dew, and frost can result in a much better or poorer wind than the year just gone. But across history, major climactic periods such as the Pleistocene, the Roman Warm Period, the Late Antique Ice Age, and the Little Ice Age of more recent centuries have fundamentally altered where grapes can flourish and with it the very history of viticulture. 
23 May 1670 – On in this day in 1670 the Grand Duke of Tuscany, Ferdinando II de Medici, died at the Pitti Palace in Florence. Back in 1654 de Medici was the first European ruler to establish a series of weather observation stations throughout his dominions and beyond, eventually patronizing weather stations as far afield as Paris and Warsaw. In doing so he began the first systematic attempt to study and monitor weather patterns across Europe in modern times. This event had an unintended consequence for viticulture. Because wine-making is so influenced by weather patterns, de Medici’s weather stations opened up an era in which viticulturists could begin monitoring how their vineyards fared in different temperatures and which grape varietals produced the best vintages in specific temperatures. Today this is a type of climate and weather science is a given in viticulture, but in the mid-seventeenth century de Medici’s idea of consistently monitoring weather patterns was revolutionary.
1 February 1999 – On this day in 1999 a study was published in the academic journal Nature which hypothesized the idea of the so-called Roman Warm Period. This presented extensive scientific evidence to suggest that the period in world history corresponding with the rise and pre-eminence of the Roman Republic and Roman Empire, roughly between 300 BC and 400 AD, was a period of particularly warm global temperatures, probably closely paralleling global temperatures in the nineteenth century. This Roman Warm Period would have produced ideal climactic conditions for viticulture to flourish in much of the Mediterranean world around which the Roman Empire was centered. Thus, the centrality of wine to Roman life was in many ways a by-product of the Roman Warm Period. Without it viticulture on the scale which the Romans practiced it would not have been possible and alternative types of alcohol would have been favored to a greater extent. This is just one of the many crucial ways in which broad weather patterns across time have impacted global wine history.
 Giancarlo G. Bianchi and Nicholas I. McCave, ‘Holocene Periodicity in North Atlantic Climate and Deep-Ocean Flow South of Iceland’, in Nature, Vol. 397, No. 6719 (February, 1999), pp. 515–517.
 Daniel Fuks, ‘The rise and fall of viticulture in the Late Antique Negev Highlands reconstructed from archaeobotanical and ceramic data’, in Proceedings of the Natural Academy of Sciences, Vol. 117 (2020).
 Peter Steen Henriksen, Sandie Holst and Karin Frei, ‘Iron and Viking Age Grapes from Denmark’, in Danish Journal of Archaeology, Vol. 6, No. 1 (March, 2017), pp. 3–10.
 Brain Fagan, The Little Ice Age: How Climate Made History, 1300–1850 (London, 2001); Geoffrey Parker, Global Crisis: War, Climate Change and Catastrophe in the Seventeenth Century (Yale, 2013); Sam White, A Cold Welcome: The Little Ice Age and Europe’s Encounter with North America (Cambridge, 2017).