In article ,
Norman writes:
John Hall wrote:

On second thoughts my suggestion would probably still over-emphasise
snowfall in relation to temperature, as the number of days of snow lying
can be anywhere between zero and 60-70, whereas the limits on winter
mean temperature are probably between about zero and 6-7. So the range
of values of the former is about ten times that of the latter. To
compensate for that, a possible index might be L - 10*T. So a very mild
and non-snowy winter would have a value of about -60 or -70, and a very
cold and snowy one like 1962-3 would have a value of +60 or +70. An
average winter would be about 10 - 10*4 = -30. If you'd rather the
average index was close to zero you could use 30 + L - 10*T.

Sorry John, I can't agree with that. Using the temperature expressed in deg C
in this way is akin to saying that a day with a max of 4 deg C is twice as warm
as a day with a max of 2 deg C which, I think you would agree, is nonsense.

I agree if you consider the temperature in isolation. And the effect if
you divide one value by the other would clearly be totally wrong. But I
don't think it's a problem with the formula above, because the constant
of 10 has been chosen to be compatible with the possible range of values
and because the lower end of the range of possible values happens, very
conveniently, to be zero. When I have time I'll use Scott's values of L
and T with my formula to see what the table would become and if it looks
reasonable.

I now see that Gavino has said that much more clearly than I've managed.
My thanks to him.

Using deg K is the only valid method. The new spreadsheet that Scott has
devised does appear to show a realistic spread in the relative severity of
individual winters.

I haven't seen the results using K temperatures yet, but it seems to me
that they would lead to the importance of temperature to be
underestimated compared to the number of days with snow lying. If
there's a problem it will only show up for the occasional winters that
are mild overall but still have a large number of days of snow and those
that are cold but non-snowy.
--
John Hall "He crams with cans of poisoned meat
The subjects of the King,
And when they die by thousands G.K.Chesterton:
Why, he laughs like anything." from "Song Against Grocers"