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A 400-year-old weather forecast could now come true in July 2026. The signs seem right, especially for Munich.
Can a 400-year-old calendar predict the weather? In July 2026, the so-called centennial calendar will provide a surprisingly adequate forecast for at least some parts of Germany. It predicts wet weather for the week of July 14 to 20, and current weather forecasts for several German cities paint a similar picture. This gives reason to take a closer look at the old calendar and its statements for this month and classify them.
A 400-year-old weather forecast is now coming true in July: the signs are correct, especially in Munich. © IMAGO / ZUMA Press Wire
The centenary calendar predicts clear and rainy weather for most of Germany between July 14 and July 20. Further, from July 21 to July 26, the weather will be fine during the day and cool and frosty at night. From July 27 to 28, the calendar predicts thunderstorms and rain before the month ends with very warm weather. A look at five major cities in Germany shows whether these forecasts are in line with the current weather situation. The dog days are approaching in July, with an old farm rule promising “bleak prospects for the rest of the year.”
Centennial calendar: what does the weather forecast for July 2026 mean?
In Munich, the current forecast for the days from July 14 shows rain or thunderstorms almost every day with a maximum temperature of 25 to 28 degrees. Agreement with the calendar forecast is most pronounced here. Berlin is also expecting mostly light rain in the second half of the week. Hamburg is off to an even friendlier start to the week before showers begin on Thursday. In Cologne and Frankfurt it will be sunny at first with temperatures up to 33 degrees, but volatility will set in from Friday.
What is a centennial calendar?
The centennial calendar dates back to the Franconian Cistercian abbot Mauritius Knauer (1613/14–1664). He observed the weather from 1652 to 1658 and organized his findings according to astrological planetary cycles. The work was first printed in 1701 by Dr. Christoph von Helwig. From a meteorological point of view, the calendar is considered unscientific, but as a cultural property it is still very popular today.
Forecasts for July 2026
July 1-3: “extreme heat”
July 4-5: “big thunder and rain”
July 6-7: “Heywater”
from 8 to 12 July: “rainy weather”
July 13: “beautiful day”
July 14-20: “rainy weather”
July 21-26: “Beautiful during the day, but cool and frosty at night”
July 27-28: “Thunder and Rain”
July 29-31: “very warm”
From a scientific point of view, this coincidence is purely coincidental. The centennial calendar is based not on meteorological findings, but on astrological ideas: its author assumed that the seven planets known at that time controlled the weather in a seven-year rhythm. These assumptions have been clearly refuted by modern science. On the other hand, current weather forecasts are based on satellite data, physical models and high-performance computers. Unlike the centennial calendar, one of the world’s strictest agricultural regulations will now make its final decision in the summer of 2026.
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However, many people who enjoy agricultural rules and traditional weather knowledge continue to closely follow the centennial calendar. For them, it is not a scientific instrument, but an object of cultural heritage that forces comparison year after year. The question of whether the calendar is correct or incorrect in a particular month is more of an ethnographic interest than a claim to a serious meteorological forecast. If you want to know if an umbrella is advisable this week, you’ll be much better off using the current weather forecast. The keyword “heat wave” is now back in the spotlight.