What do the forecast time periods signify, centre or start

[pete_run]

This might seem a simple question, but I've noticed this problem on most weather forecast sites, and never found an answer in any of their "helps".

The block of times are usually given in 3 hour segments. i.e.

09:00 - 12:00 - 15:00 - 18:00 - 21:00

But does the 12:00 signify the centre of the time period, or the start (so it would show details for 1200 through 1500?

[Shiny_Bottom_1]

At a guess, if only a single time is stated (i.e. 12.00), I would say it is for that time period.

[Cat 5]

I would agree with Chris. The proposed time is the anticipated weather conditions at that percise time and not necessarily the time before / after.

By giving 3 hour indicators you can use your own judgement for deterieration etc