By the Numbers
By the Numbers: England Had 3% of Average July Rainfall
Explain why 3% of average rainfall means a 97% shortfall, using clear illustrative millimetre examples.
The Environment Agency reported that England had received only 3% of its long-term average July rainfall at the time of its 21 July drought update.
That wording contains a common percentage trap. “3% of average” means the observed amount is a small fraction of the benchmark. It is not the same as “3% below average.”
The story number
The Environment Agency's National Drought Group update said:
- England had received 3% of its long-term average July rainfall
- the south and east had received no rain so far that month
- eight areas were in prolonged dry weather
The agency also published its rainfall and river flow summary for 15 to 21 July 2026 on 23 July.
The number to run
If observed rainfall is 3% of a long-term average:
`observed amount = long-term average Ă— 0.03`
The percentage shortfall is:
`100% - 3% = 97%`
So “3% of average” is equivalent to a 97% shortfall from average.
The assumptions
The Environment Agency statement gives the national percentage, not one universal millimetre total for every location.
To show the arithmetic, we use three explicitly illustrative long-term July averages:
- 50mm
- 60mm
- 75mm
These are teaching inputs, not official values for England or a specific weather station.
Run the numbers
| Illustrative long-term July average | 3% of average | Shortfall |
|---|---|---|
| 50mm | 1.5mm | 48.5mm |
| 60mm | 1.8mm | 58.2mm |
| 75mm | 2.25mm | 72.75mm |
For the 60mm example:
- 60 Ă— 3% = 1.8mm observed
- 60 - 1.8 = 58.2mm shortfall
- 58.2 Ă· 60 Ă— 100 = 97% below the benchmark
Why “of” and “below” differ
Consider a less extreme example:
- 80% of average means 20% below average.
- 20% of average means 80% below average.
- 3% of average means 97% below average.
The two percentages add to 100% because one is the portion observed and the other is the missing portion relative to the benchmark.
Saying “rainfall was down 3%” would describe a much smaller change: 97% of average remained. That is the opposite of the Environment Agency's 3%-of-average statement.
What the result means
The percentage describes England's month-to-date rainfall compared with a long-term July benchmark at the point of publication. It does not mean:
- every place recorded the same percentage
- July had finished
- a specific garden, river or reservoir was at 3% capacity
- the percentage alone predicts what happens next
It is a comparison of rainfall over a defined period with a historical reference.
Try your own numbers
Enter 3% and a hypothetical baseline in the Percentage Calculator. Then subtract that result from the baseline to see the shortfall.
The Average Calculator can help summarise a set of monthly rainfall totals. The Standard Deviation Calculator can show whether those historical values are tightly grouped or highly variable.
Caveats and source notes
- The 3% figure was a national, month-to-date statement made before July ended.
- Regional and local totals differed; the south and east were specifically reported as having no rain at that point.
- Long-term averages depend on geography, reference period and measurement method.
- The millimetre examples above are illustrative and must not be presented as official England totals.
Sources: Environment Agency, National Drought Group steps up response after third heatwave, 21 July 2026; Rainfall and river flow weekly reports for England, updated 23 July 2026.
