Are More 100 Year Storm Happening? Yes and No. A Proliferation of Rain Gauges Can Now Record More 100 Year Storms, But Fixed Locations Show No Increase

There are many sensational media stories about ghost storms and ninja storms hitting urban areas, and a steady claim that we are experiencing more extreme rainfall, that is, higher intensities for a given probability (called return period), or greater frequency of given design intensities. Often it is stated that we are experiencing more 100 year storms today and that is a "new normal" brought on by a changing climate.

How does the number of climate stations, or rain gauges, that are in operation affect the number of observed extreme events. Well, let's look at Toronto for example.  Several past extreme events were reported in the Staff Report on Impact of July 8, 2013 storm on the City's Sewer and Stormwater Systems dated September 6, 2016: (

During the May 12, 2000 extreme rainfall event, Toronto operated 16 rain gauges as shown on the staff report map below.

Fifteen years later, during the August 19, 2005 storm, the City operated 31 rain gauges as shown below, so almost double the number of rain gauges.  Look at the higher density of gauges in north Toronto where many higher August 19, 2005 rainfall depths were observed.

Then 8 years later, during the July 8, 2013 storm the city operated even more rain gauges, i.e., 35 in total.

And then a few years later, on August 7, 2018, the city operated 43 rain gauges - even more than 2013. I don't have a map but here is a super-cool graph summarizing Toronto Open Data rainfall totals at those gauges over a period of 5 minutes to 24 hours.

And now today as of July 17, 2019, Toronto has 45 active rain gauges as shown in the following map presented to the Ministry of Environment Conservation and Parks' stormwater stakeholder group participating in development of minimum standards for ECA pre-approval.

So let us summarize the trend in the number of rain gauges in the chart below.

Astute blog readers will notice that the number of rain gauges has increased almost 300% since the year 2000. Yes, almost three times the number of rain gauges now. Obviously, more extreme events can be observed and recorded when the number of rain gauges increases dramatically.

The following table shows that in the year 2000, there was a rain gauge every 39.4 square kilometres (16 gauges per 630.2 square kilometres). By 2019, there is a gauge ever 14 square kilometres.


So what is happening at fixed locations where rain intensities are measured? In Toronto and Mississauga, many trends are downward according to the Engineering Climate Datasets:


As a result, design intensities for short durations have been decreasing since 1990:


To recap, many more rain gauges today mean we 'see' more storms - these are typically needed to support basement flooding Municipal Class EA studies (rainfall needed to calibrate hydrologic and hydraulic simulation models), to guide operational activities too.  Many municipalities have installed rain gauges to support inflow and infiltration management programs.

We have a "finer mesh net" to catch these events and add them to our records - we have almost 3 times more rain gauges in Toronto since 2000.

But no. Storm are not becoming more intense. If we see more of them, it is because we are looking harder for them with more extensive monitoring efforts. Given this expanding intensive network of rain gauges today, it is not uncommon, statistically speaking, to observe many 100-year storms over a short time period.  This earlier post explores those statistics in the GTA -


  1. It is my first visit to your blog, and I am very impressed with the articles that you serve. Give adequate knowledge for me. Thank you for sharing useful material. I will be back for the more great post.
    hợp đồng bảo hiểm ô tô

  2. I am very impressed with the articles that you serve
    bảo hiểm tai nạn giao thông

  3. Thanks for moving the conversation along.

  4. Another astounding thing about utilizing programmed yet this conclusions or moves to pay yourself initially is that you can utilize it to turn into a tycoon—consequently. This may sound insane, however it more info really works. On the off chance that somebody naturally had $200 moved from every one of their fortnightly paychecks into their speculation account from some info when they were 25 until they were 65, they would wind up with over $1,000,000 on the off chance that they found the middle value of a 7% pace of profit for their ventures. So an ordinary individual can turn into a tycoon naturally without winning the lottery. This arrangement would require somewhat more penance than the vast majority are eager to make in their twenties, however it is more info completely conceivable. Presently you realize how to turn into a mogul… ..if just you were 25 once more. The absolute best strategy to setting aside info cash is to make a Spending Plan or a Budget (figure out how to make a financial limit). With a spending you make sense of what your salary is and what your costs are. When you know these two things, you can search for approaches to diminish your costs or increment your salary to assign a measure of cash that you can stand to spare. This is the manner some more info by which the world's biggest companies do it and this is the means by which a large portion of the world's fruitful agents do it. This technique takes a tad of work toward the start and a registration consistently or two, yet it works.

  5. Yes i am totally agreed with this article and i just want say that this article is very nice and very informative article.I will make sure to be reading your blog more. You made a good point but I can't help but wonder, what about the other side? !!!!!!Thanks storm damage repair

  6. Very informative post! There is a lot of information here that can help any business get started with a successful social networking campaign. Arbor Care Solutions

  7. Natural Herbal Medicine To Cure {HERPES DISEASE} TOTALLY HERE
    Do you need a solution to cure your Herpes Disease contact Chief Dr Lucky to help and he will surely help you to cure your Herpes Virus .. I have suffered from Herpes-2 Virus for 4years ago that almost took my life. But one day I was searching the internet and I found Chief Dr Lucky saw so many testimonies on how Chief Dr Lucky helps people in curing their deadly diseases, and I contacted Chief Dr Lucky, asked him for solutions and he started the remedies for my health. He prepared herbal medicine for me and I received the herbal medicine and after using it for 2 weeks my condition has greatly improved, all my symptoms including Abdominal pain, Nausea and vomiting, Loss of appetite stopped, so I went to my doc and was confirmed negative. I am Herpes Virus free! contact the herbal doctor via his email> also visit his page> or his cell number / WhatsApp> +2348132777335 Website >


Note: Only a member of this blog may post a comment.