Events can be arranged in a circle and still occur only once.
The reference was to the expectation among forecasters that in any given 1,000 years, such flooding could reasonably be expected to occur only once.
The government is reviewing its flood risk data after repeated extreme weather events of the kind that supposedly should occur only once in many decades.
Practicing physicians are only dimly aware of many of these disorders, some of which occur only once in as many as several hundred thousand births.
Give them an analogy too — the idea, for instance, that winning that same lottery is likely to occur only once every 270,000 years.
The term "100-year storm" doesn't mean, as many people believe it does, that such a storm will occur only once in a century.
A flood of such magnitude that it might be expected to occur only once in 100 years is called a 100-year flood.
Vectors have target sites for many different restriction enzymes, but the most convenient ones are those that occur only once in the vector molecule.
Noaa considers these floods extreme because, based on historical rainfall records, they should be expected to occur only once every 500 years.
A huge area west of Houston was impacted by rainfall amounts that occur only once every 100 to 200 years, on average.
Such storms generally occur only once or twice a year, as they require very specific conditions to form, including a mass of cold air and atmospheric instability.
