Sorry, but 26C is not “cool for swimming”. Well, I mean if it was 26C it would be cool (in the sense of neat) if I could go swimming, but really, what?
The metric system was always easy and self-explanatory. Fucking conversions, which required us to take some goddam measurement in inches and convert to centimeters or in kilograms and convert to pounds, that was the stuff they made us wade through over and over in elementary school and I’m sure it left a bad taste in a lot of Americans’ heads. American unit conversions may be awful (12 of this, 3 of that, 16 here, 2 there, four here, etc) but they’re rarely as awful as 2.2 or 1.6 or subtract 32 then multiply by 5/9, I mean yeesh.
The remaining hostility is probably just due to “I know a yard when I see it and I can tell you what 25 pounds feels like but I have no freaking intuitive sense of a centimeter or a kilogram so don’t give me that metric shit”, plus a double scoop of rah rah rah USA USA bullshit.
There are a few reference points that might help those who want to get a better feel for metric units. One dollar bill is one gram (who gives a rat’s ass about paper clips?). So is any U.S. bill. One liter of water is one kilo, so a 2 liter Coke is a bit more than two kilos. A half kilo is a little more than a pound, maybe a couple bites if a sandwich is the example. Thirty cm is close to a foot for guesstimate purposes, and a meter is a little longer than a yard. 50 mi/h is just about 80 km/h, so a km is about 5/8 of a mile.
There. Everybody feel better now?
By which you mean that you’re comfortable swimming when it’s 26 out? OK, but for most of us, that would in fact be a bit on the cool side.
In Australia, we converted from Imperial to metric when I were just a lad. So I had a lot of imperials already hard-wired into me. The conversion process took some years and many signs were double printed in both units for a while.
I’m nearly right with all of them by now. Temperature, car speed limits, lengths and distances - these we use nearly every day, and so you learn them or you struggle. Weights - OK. But height? Nup - just a blank spot. I know I’m about 5’9" - if someone says ‘he’s about 175 cms’ I have no idea - even though that’s the same. I know how tall a 6-footer is, I know 6’4" is quite tall and under 5’ is very short even for a woman. But give me those heights in metric and I’m lost.
Police are looking for a 183cm man with a Seahawks hoodie and black jeans. 
This, THIS, THIS!
One of the funniest things I’ve ever seen in my life was when a couple of us were trying to convert a new recipe in the restaurant from metric to English. We were trying to figure out how many grams of some spice equalled the eighth of an ounce that we normally measured. "Three point five grams! blurted out the assistant manager, who was also one of the biggest stoners we knew. Since this was a pizza place…that should say something. All of us started roaring with laughter, "What? What? I just knew that, man. It don’t mean I’m a pothead or nuthin’ ]
Turquoise & bilious green, *plus *black? The fashion police are certainly looking for him if nothing else. 
Speed limits and long distances really aren’t that bad. 100 kph is about 60 mph, decent highway speed, if a little slow. No big deal, regardless; so what if you get there slightly faster than you estimate.
In U.S. units, the distance in miles is roughly the number of minutes to your destination. Anywhere else, divide the kilometers by 100 to get the number of hours to your destination. (For longer distances, the number of hours is more useful, IMHO).
Want to convert? No problem. In the U.S., they show both units on most all speedometers - must be so in Canada as well. The conversion from miles to kilometers and back is the same as the conversion between mph and kph - it’s right there on the dial.