Alberta flood feature: Why does Calgary get so much rain in June?

CBC Calgary weather specialist Craig Larkins explains the weather conditions that make June soggy.

CBC Calgary weather specialist Craig Larkins gives 3 factors that help produce heavy rainfall each year

A couple walk along the swollen banks of the Elbow River in Calgary during last year's flood. (Jeff McIntosh/Canadian Press)

In the world of weather, June can be labelled the "transition" month from spring to summer.

Call it a changeover of the seasons. During this changeover, there are three key factors that influence our weather.

First, it's the time of the year when moisture-packed weather systems originate in the Pacific Ocean and make their way into southern Alberta — and the southern Prairies for that matter.

One of the reasons we see this pattern develop during June is the annual northward progression of the jet stream. It acts like a steering mechanism for systems from the Pacific as they move eastward.

Another contributing factor to June's wet weather is the foothills and mountains of the Canadian Rockies. The topography is ripe for the creation of thunderstorms. The elevation changes in mountains and foothills are the "ingredients" needed for thunderstorm development which adds to rainfall totals.  

Finally, as temperatures rise during June, daytime heating creates early afternoon clouds which can lead to late day showers or thunderstorms.

It's a trend that has become all too familiar with Albertans: a sunny start to the day with a chance of thunderstorms to end it. Daytime heating isn't just a June weather factor, it also contributes to storms we may see in July and August.

Southern Alberta is no stranger to record rainfall and flooding at this time of year. 

The chart below illustrates the worst floods in Calgary over the past 117 years. The common theme is that most of the rain came in the month of June.

It's important to be vigilant now that we are well into the "June Monsoon" season in Calgary. Remember flood mitigation efforts even at the smallest level: clean your eaves troughs, make sure drain pipes are pointed away from your home and seal leaky windows. 

But also remember that June can be the most beautiful month of the year in our city as grass turns green, the leaves come out, and the flowers bloom. Enjoy! 


Craig Larkins

CBC Calgary weather specialist

Whether it's wading waist deep in floodwaters or reporting live from the centre of a wicked blizzard, Craig Larkins delivers the forecast with a friendly ease that relates to everyday families. He provides up-to-the-minute information to help them face the day.


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