"Bernard Burton" wrote in message
...
Alastair, you need to be a little cautious when trying to deduce trends or
cycles using running averages. It is a mathematical fact that any series of
unweighted means will show periodic fluctuations with a period two to three
times the averaging period. The effect has been discussed several times in
'Weather', (Burton June 1997, p195, Reynolds Weather 1978, pp 74-76).
Running averages of random numbers will produce some really convincing
cycles.

Of course, here there is not a cycle, but a linear trend,but it is probably
just a coincidence. If not, then we can predict the average temperature
in the first 10 days of June next year by calculating the running mean for
next year, by adding 0.1C to this years mean, and then determining what
temperature next year would give that mean.

Of course why restrict it to only 10 days in June? Next June's average
temperture could be calculated that way, and all other months as well!

Cheers, Alastair.