"Harry Bloomfield" wrote in message
news
whisky-dave expressed precisely :
When they explained it on the TV durign a weather documentary they said
it wass the chance of rain andn showed how they calculated it.
In waether there';s a few things that can happen due to changign Highs
and lows and various 'gulf' type streams the forcaster can guess which
will effect which but it's a probabilty rather than a known outcome, so
they use the % term.

I suppose they could use odds like bookies.

I was wondering about that yesterday, reading the local forecast. It was
showing various percentages for each hour, 20%, 30%, 40%, 70%. Even
threats of thunderstorms. Does the first 20% mean that there is a 20% risk
of some rain within that hour,

Yep.

or something else?

Nope.

In fact what happened was someone 2 miles away saw some brief and light
rain, hardly worth a mention.

Sure, but that's why it said 20% etc and not 100%

We had cloudy, no rain fell at all, no thunder, the sun came out when it
was supposed to be 70%

That's why it said 70% and not 100%

and it was hot and very humid.