On 25/07/2017 19:18, James Wilkinson Sword wrote:
On Tue, 25 Jul 2017 11:55:29 +0100, whisky-dave
wrote:

On Thursday, 20 July 2017 20:38:25 UTC+1, James Wilkinson Sword wrote:
On Thu, 20 Jul 2017 16:08:28 +0100, NY wrote:

"James Wilkinson Sword" wrote in message
news What do you believe weather forecasters mean when they say "40%
chance of
rain"?

1) It will rain for 40% of the day.
2) There's a 40% chance it will rain at some point.

I googled it and apparently it depends on the forecaster? 1) and
2) are
completely different meanings.

Given that it includes the word "chance" (ie probability) I'd
interpret it
as the second meaning: if (hypothetically) you replayed the day
many times
(Groundhog Day!) then approx 40% of the occurrences of the day
would have
some rain.

Which is of no use to me whatsoever. Pouring with rain all day is
nothing like spitting for half an hour. Yet they don't distinguish
between the two.

How about showers or inteminant showers or heavy downfalls, storms.

Yes, those are more helpful. But "20% chance of rain" means nothing,

There should be a measurement where 0% means no rain at all, and 100%
means rain all day.

So what would 50% mean light showers for 50% of the day or heavy rain
50% of the day, and whayt would the other 50% be of the day be like ?

If there's only a % number it should be expressed as a percentage of
pouring all day.

But is 50% pouring all morning and dry all afternoon or alternating
between pouring and dry every hour?

The weather app that I use on my phone gives me a percentage chance of
rain for each hour of the day and a symbol next to it for bright
sunshine, partial sunshine, overcast, light rain, heavy rain, downpour
or thunderstorm.

SteveW