The Dog Days of Medieval Summer
As July approaches, some people look forward with anticipation to the heat of summer, others regard it with something closer to dread. Summers in Britain are getting hotter, with heat records repeatedly broken over the past few years, and for some the health consequences of sustained high temperatures can be serious. Any medieval physician could have warned you that summer heat is not something to treat lightly; as they thought about it, July and August were perhaps the most dangerous time of year for human health.
This was because mid-July sees the beginning of the dog days of summer, which take their name from the period when the Dog Star Sirius, brightest in the night sky, is visible above the horizon. Since ancient times this change in the heavens has been associated with a perilous season on the earth: in Greek and Roman astronomy, the sultry dog days were believed to be a time of plague, fevers and physical lethargy. In the Iliad the Dog Star is ‘a portent of suffering, bringing with it fever for wretched mortals’.
Since these beliefs originated in cultures around the Mediterranean, we might expect them to have less relevance in colder and more northerly climates. However, information about the dog days was widely disseminated throughout Europe in the medieval and early modern period. For writers learned in medicine and astronomy, the dangers of the dog days were standard knowledge; their dating was frequently included in calendars and almanacs, and they even appear in the calendar of the 1552 Book of Common Prayer. There were different traditions about when the dog days began, but they typically lasted from the second or third week in July until early September.
Information on the dog days was not just a curiosity, but was believed to be of practical use because of the link between climate and health. One of the most important medical manuscripts from early medieval England, the tenth-century Bald’s Leechbook, warns:
Fifteen nights before Lammas [1 August] and thirty-five nights afterwards bloodletting is to be avoided, because at that time all venomous things fly and greatly injure human beings. The wisest physicians have taught that in this month no one should drink medicine, or in any way weaken his body, unless it is absolutely necessary, and in that case he should stay inside around the middle of the day, because at that time the air is most impure. For this reason the Romans and all southern peoples made earth houses for themselves, because of the heat and poison of the air. Physicians also say that growing herbs are best to prepare at this time, whether for potions, salves, or powder.
This is based on classical sources, as the reference to ‘the Romans and all southern peoples’ makes clear, but it is treated as if applicable to the British climate too. Bald’s description suggests that this season is not all bad news: while it may be dangerous for health, it is also a good time for preparing herbs for future medicinal use, laying in stores during the summer for the year ahead.
Centuries later, early modern writers were still warning against bloodletting and taking any risks with health in this season. Along with the threat to the body, there were also fears that the heat of the dog days could cause irrational behaviour, violence and unrest. That belief seems to underlie one famous fictional evocation of the dog days, Romeo and Juliet. This play, as we learn from a conversation between Juliet’s nurse and Lady Capulet, is specifically set in mid-July: it is ‘a fortnight and odd days’ before Lammas Eve, Juliet’s 14th birthday, so firmly in the dog days. Like the classical and medieval authorities, Shakespeare’s contemporaries associated this period with madness and the most dangerous heat of summer – one explanation for the violent passions of love and hatred which power the tragedy of the play.
By counting time backwards from Lammas, the first harvest festival of the year, Romeo and Juliet uses the same language as Bald’s Leechbook some 600 years earlier; though the tragic passions of the play are kindled by the heat of an Italian summer, this reference implies a more homely British context too.
The British summer, as we are used to thinking about it, is more a contradiction in terms than a serious threat to health, but things are changing. Perhaps we should listen to this ancient tradition, and start taking the hot season more seriously.
Eleanor Parker is Lecturer in Medieval English Literature at Brasenose College, Oxford and the author of Conquered: The Last Children of Anglo-Saxon England (Bloomsbury, 2022).
