May 22, 2026
Wet Days in Grey and Bruce Counties
By John Anderson, 2026
MEASURING PRECIPITATION
Measuring of precipitation is one of the most important weather observations climate scientists make. Precipitation falls as rain when it is warm and as snow when it is cold. Sometimes we get both during a day! Together, they add up to total precipitation.
Some days we can get a lot of precipitation – scientists call these extreme weather events (Figure 1). Such wet day events can overwhelm our natural and human built systems – rivers overflow their banks and buildings flood. People in the insurance business refer to such events as catastrophic loses.
Figure 1. Cartoon image of flooding in Toronto 2013. Original source picture was CBC news. Image created using ChatGPT (OpenAI 2026).
Normal annual precipitation has increased by nearly one-third since the 1950s — and what we call ‘normal‘ keeps changing.
NORMAL CONDITIONS
Normal weather conditions are measured over thirty-year periods. This is considered by scientists to be the shortest time period over which we can measure the climate. Every ten years, this estimate is moved forward to reflect how our climate might have changed. For example, in 2026 our normal period is calculated from 1991 to 2020. On January 1, 2031 the new normal period will be re-calculated from 2001 to 2030.
ANNUAL PRECIPITATION
Annual precipitation in Grey and Bruce Counties has been steadily increasing for decades (Figure 2). In the 1950s, normal annual precipitation was 844 millimeters each year. Today, that ‘normal’ has risen to 1,111 millimeters – a 32% increase. For people born in this decade, today’s wetter conditions feel perfectly normal, because for them, they are! But consider what this shift looks like to someone born in the 1950s. The new normal represents a striking shift from what they once knew.
Figure 2. Normal precipitation in Grey County has risen steadily since the 1950s and is now 33% higher.
WET DAYS
Scientists have different ways of measuring wet day events. One of these measures the maximum amount of precipitation we receive over a five-day period each year.
Have wet day events increased in Grey County from 1990 to 2025? Two estimates of wet day events were examined: the first was the maximum amount of precipitation received each year over a five-day period. The second, was the frequency of five-days that equalled or exceeded a total of 50 mm weather.
Both are indices of extreme weather.
Extreme Wet Day events have doubled over thirty years — and the trend shows no sign of slowing.
To simplify, results were averaged for three decades – the 1990s, 2000s, and 2010s. Maximum five-day precipitation gradually increased over time, averaging 67 mm, 71 mm and 81 mm, respectively. Compared to the 1990s, we now get 21% more precipitation during our maximum five-day events.
The number of extreme wet day events has almost doubled over the past three decades – from an average of eight per year in the 1990s to more than fifteen per year in the 2010s (Figure 3). This is a statistically significant upward trend of roughly one additional extreme five-day event every three years. Given this trend we can expect an average of 21 events in the 2020s.
Figure 3 – Decadal averages of the number of days each year when total precipitation over five-day periods equalled or exceeded 50 mm.
CLIMATE CHANGE
What is driving the increase in extreme wet days in Grey and Bruce? For each one-degree Celsius increase in air temperature, the atmosphere can hold about 7% more moisture. In addition, as we experience declining ice cover on our lakes there is more open water that increases evaporation.
Scientists predict that temperature and precipitation will continue to increase as the planet warms due to climate change. Not only can we expect to get more precipitation, we can also expect to get a lot more wet day events that will challenge our existing infrastructures – roads and bridges, buildings, and watersheds.
CLIMATE CHAOS
While our precipitation is increasing steadily, the frequency of extreme wet day events is increasing much faster. The high year-to-year variability in wet day events — some years bring just a handful, others bring more than thirty — is itself a sign of increasing weather instability.
When precipitation falls, it can come down as rain, snow, freezing rain or hail. Wet day events are often associated with storms that bring high winds and lightning. The Insurance Bureau of Canada records show that, since the early 1980s, seven of the top ten payouts due to catastrophic weather were due to flooding, hail and freezing rain.
ADAPTING TO THE NEW WEATHER
People in Grey and Bruce are starting to experience climate change as we trend towards conditions people living here have never experienced. This will require significant and ongoing adaptation (Figure 4).
This is a story about how each of us, in our own way, will have to adapt to the new reality of more precipitation, more wet day events. Many people and organizations are adapting to these new conditions. We invite you to explore their stories in our Grey Roots Museum exhibit, Local Stories: Changing Weather, part of the Wild Weather exhibition which runs from May 16, 2026 to September 5, 2026. Each of us has a role to play in building a more resilient future for Grey and Bruce.
Figure 4. Cartoon image of school children trying to go to school when it has flooded. Image generated using ChatGPT (OpenAI 2026).