Dead right Graham - a meteorological drought.

Wikipedia says this about the 'old' definition:

"A drought was defined as 15 consecutive days with less than 0.25mm (0.01 inches) rain on any one day"

and as far as I can see it says this is the new improved version:

"A drought is usually defined as an extended period of weather (usually around 3 weeks) where less than a third of the usual precipitation falls"

As far as I can see the old method is very clear and the new method totally ambiguous with the use of the word "around" very imprecise...