An improvement in the weather

A recent exchange of e-mails between Ezra, a reader of MetricViews in the USA, and Tony, in the UK, suggests that recent years have seen changes for the better in weather reporting in the both the UK and Canada. Do other readers of MetricViews share Tony’s viewpoint?

Ezra wrote on 27 February:

“I just posted this comment to the USMA mailing list. My encounter with Canadian metric weather reports makes me wonder if this is one area (other than road signs) where Canada is ahead of the UK in terms of metrication. Can you enlighten me?

I just happened to check out an article in the Vancouver (Canada) Sun online and noticed the link for the current weather, so I thought I’d have a look.

You can choose many different  countries and cities within each country, so I tried where I live (Seattle area):

I notice that everything is given in proper SI (except for wind speed, which is in km/h rather than m/s, but I’ll take it anyway, especially since they use the proper syntax instead of some monstrosity like “kph”), including the use of kPa for barometric pressure. And there is no option I could find to switch to Imperial!

I’ve seen Canadian national weather reports on the CBC and the story is the same – not a whisper of Imperial anywhere.”

Tony replied:

“As I understand it, Canada uses Celsius only with the exception of the Windsor area (where the US influence is very strong due to many working over the border) and in cooking where F lingers due to old habits/recipes and US influence. Canadian ovens generally dual labelled for sale across N America while ours are Celsius only.

In the UK, Celsius has been used for many years (see UKMA’s YouTube channel,, for a news clip on Kennedy’s assassination; it starts with a weather report which gives temps in Celsius first, F second, although the term centigrade was used).

So Celsius is well embedded in the UK and is without doubt the principal unit used, but Fahrenheit lingers on as secondary units in certain places, such as papers with a more elderly following. Personally I almost never hear or read any Fahrenheit anywhere as they don’t use it at all in the papers I read or radio stations I listen to, but others may hear more imperial if they read other papers and listen to other radio or TV broadcasts.

Rain is given in mm, and snow generally in cm, although inches also sometimes used for snow in forecasts or news reports. Wind speeds usually quoted in mph, as that’s the only measure of speed most people know due to road signs. Main exception is in sports such as athletics where m/s is used; times only count as records if wind is under 2 m/s so that’s why that measure is used there.

Pressure in kPa rare I think, but used on the Met Office website.”

Ezra responded:

“I had heard that Celsius was regularly used in the UK for cold weather reports and Fahrenheit in the summer time because the latter numbers are larger! It struck me as a strange and jarring way of doing business, but it sounds like that report is untrue.

If all ovens sold in the UK show Celsius only, then those who have cook books showing just Fahrenheit for baking or oven cooking temperatures need to consult a conversion chart, I presume. (I hope nothing like that comes affixed to the oven, itself!)

If kilopascals are not used for barometric pressure, do you folks use millibars or inches of mercury on television, radio, and in the newspapers?

As for wind speeds in mph, we see once again the pernicious effects of having failed to convert the road signs long ago as originally planned. It is striking how a single decision can have such far-reaching effects down the road (if you’ll pardon the pun!)

Let us hope that the rising concerns for safety (drug dosages, malnutrition in patients, bridge strikes, speeding by lorry drivers from the Continent who have km/h-only speedometers in their vehicles, etc.) can be parlayed into a general recognition on the part of the government that finishing metrication (including conversion of all road signs) should be delayed no longer.”

Tony brought the exchange to a close:

“Regarding Fahrenheit in hot weather, it certainly used to be the case that the media would hype hot temperatures in Fahrenheit in summer just because it sounds more extreme. But such usage has receded significantly in recent years as they have realised that hardly anyone under 50 knew what they were talking about; see these articles on the same topic, from the same newspaper:

From 2003 to 2009 you’ll see that the articles have gone from dual unit (with hyped F headlines) to Celsius only. And there was a front page headline in the same paper which I can’t find (but is mentioned here which quoted the recorded highs of 52C and 47C on London buses and tubes in 2006, so extreme highs are now much more likely to be in Celsius.

Regarding ovens, I have never seen an oven in the UK with Fahrenheit markings, nor a recipe book with only Fahrenheit (though older books tend to have both scales), so the change happened long ago.

On pressure, millibars are used.

Visibility (which I forgot to mention) is given in km; it’s not something used in mainstream forecasts but where it is given I have only ever seen or heard it in km. See here for example:
(Although that site does contradict something else I said in giving wind speed in km/h!)”

11 thoughts on “An improvement in the weather”

  1. In my experience national BBC weather presenters hardly ever mention Fahrenheit but regional presenters do occasionally.

    Clearly they only do so as a token gesture.

    If any viewers and listeners really depended on F for a proper understanding of weather reports they’d have a hard time, which strongly suggests that those who complain are motivated by concerns other than genuine comprehension.


  2. I don’t watch the weather but I do go on the BBC weather website. For a while they had toggle buttons displaying KPH and wind speeds displayed in KPH. I did email them to change to km/h. They did after a while but it didn’t last long. The button was changed back to KPH then to KM/H before going to km/h with mph changed to lowercase as well. However mph is default yet °C and mb (should really be mbar) are used. Distances from the observation stations are given in mi and km though with no space between the numbers and km.

    However the Met Office forecast does not give any options to show Metric units only. They have a mix. °C and mph and distances in m and km.

    Also, would hPa not be a better unit than kPa to replace mbar since they are equal?


  3. I was actually a little surprised at an iPhone app I downloaded recently. Provided by the UK Met Office you can switch temperature from C to F (C is the default) but wind speeds can only be shown in MPH or Knots, there is no option whatsoever for either m/s or km/h.

    Other weather apps I’ve used don’t seem to bother with wind speed so there has been no basis for comparison!


  4. There is nothing wrong with hPa in principle but would it seem natural to quote, say, a distance of 100 000 m as 1000 hm?

    The system is flexible but there is an intended heirachy of prefixes which shouldn’t be disrupted by trying to emulate legacy units.

    I think I could get used to the idea that 101 kPa is typical of fine weather and 99 kPa dull and unsettled.


  5. I was going to make the point that philh already has: that regional BBC weather reports insist on telling you the Fahrenheit comparison; it’s meaningless to most people. Again on ESPN during the Arsenal vs Man City game, the commentator said ‘It really is hot out there. Somewhere in the seventies’. Sorry, this means nothing to me and I have no idea how hot this really is (I sound like an imperial die hard complaining about metric here!).

    Anyway, get ready for more of this during the play off matches at Wembley, where no doubt it will be a scorching 100 degrees!


  6. Phil – I think if kPa was used, it would omit the small variations in air pressure. 99 kPa is quite a bit different from 101 kPa and would result in rounding of numbers whereas mbar and hPa both show small variations.

    Typically air pressue is given as four significant figures on weather forecast pages and in a 24 hour period, the air pressure will vary but this variation will not be shown using kPa. Say a day varies between 1015 to 1024 mbar, it would be shown as a consistant 102 kPa but using hPa would retain the additional units. Could use a decimal point and have it as 102.1 kPa however it will become disjointed when the .0s are omitted.

    I think the flexibility of the Metric system should be used for its full potential. 1 kPa is just 10 hPa and 1 hPa is 1 mbar.


  7. The official body for things meteorological in the UK is The Meteorological Office who give the definitive list of units to be used and their abbreviations at It is my understanding that the World Meteorological Organisation, an agency of the United Nations, ( requires that for the international exchange of wind speed data, there are three accepted options: km per hour, knot, meter per second. Note: Miles per hour are not acceptable, so why can’t the UK Met. Office show some fortitude and start using km/h.? After all, it is a trading fund agency of a government department, the Ministry of Defence, and therefore should be using metric measures as per or isn’t weather forecasting considered to have an impact on economic activity, public health and public safety?


  8. I remember as a child listening to weather bulletins on BBC Radio 4, which my mother had on regularly. Every temperature was given as “x centigrade, y fahrenheit”. I developed the impression that fahrenheit was a sub-division of centigrade – like feet and inches. That must have been 40 years ago. What has changed since then? On BBC radio, very little. They have brought the name of the “centigrade” unit up to date – though you sometimes hear the old name still, but they still seem obsessed with giving out a confusing list of numbers for every temperature. Considering Radio 4 is the BBC’s intelligent radio output it really is incredible that they persist with such un-intelligent broadcasting.


  9. Given David Brown’s post about BBC Radio 4, is there any way to probe what the rationale is behind the continued use of Fahrenheit over the airways on any of the radio and TV stations and channels associated with the BBC?


  10. In a recent case in the UK a teacher assaulted a pupil with a 3 kg dumbell. It’s obviously a very distressing case, and well reported. I was interested to note that while most press coverage referred to the 3kg weight, including BBC local news coverage, in their prime time ‘Ten o clock News’ last week, the news anchor referred to an assault by a ‘6lb’ dumb bell. So they not wrongly convert the mass of the item used, but also blatantly ignore the images from the trial which clearly shows a 3kg dumb bell! Why not just report the facts!


  11. I use metric measurements and think in metric having run a weather station using millimetres and degrees Celsius for many years. When you get used to something it becomes second nature.


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