Why Rainfall Can Vary So Much Across a Single Farm
Most farms run on the assumption that one rain gauge tells the story for the whole property. For temperature or wind, that assumption usually holds up reasonably well, conditions change gradually as you move across a paddock. Rainfall does not play by the same rules. It is the most locally variable weather parameter on a farm, and on properties of any real size, a single gauge can miss what is actually happening only a few paddocks away.
This matters more as properties get larger. The bigger the property, the more likely it spans conditions that a single gauge simply cannot represent, and rainfall is where that gap shows up first and most often.
Why Rainfall Behaves Differently to Other Weather Data
Temperature and wind are driven largely by broad-scale weather systems and terrain, so they tend to shift gradually across a property. Rainfall, particularly the convective storms that produce much of Australia's summer rain, is a different story. Convective rain forms from localised heating that builds a storm cell over a small area, and that cell can dump significant rain in one spot while leaving a paddock a few kilometres away completely dry. The same storm system can look like a flood in one corner of a property and a non-event in another.
What the Research Says About Rainfall Over Short Distances
This is not just a farming anecdote, it shows up clearly in hydrology research on dense rain gauge networks. Studies measuring how closely nearby gauges agree with each other have found that rainfall readings typically stay well correlated only within roughly 1.5 to 3 kilometres of each other, and that correlation rarely holds beyond about 5 kilometres, especially during convective events.
The effect is strongest close to a storm's core. Research on extreme convective rainfall has found that peak rainfall intensity can drop by roughly half between 1 kilometre and 5 kilometres from the most intense part of a storm cell. Widening gauge spacing further makes the gap worse again: one study comparing gauges at different spacings found the correlation between nearby readings fell from around 82% at 5 kilometres apart to just 21% at 40 kilometres apart, with the average error between gauges climbing sharply over the same range.
Two rain gauges only a few kilometres apart can record meaningfully different totals from the very same storm, particularly during convective summer rainfall. A single gauge only ever tells you what happened where the gauge is standing.
What This Looks Like on a Real Property
Picture a summer storm cell moving through. One end of the property records a solid, useful fall. The paddock at the other end, not far away as the crow flies, records a fraction of that, or nothing at all. If the only rain gauge on the property sits at one end, every irrigation, grazing or spray decision made off that single reading is being made on data that may not reflect large parts of the farm at all.
For a full breakdown of when a single station is enough and when it makes sense to add more monitoring points, including how terrain, crop type and spray operations factor in, see our guide on how many weather stations your farm actually needs.
Where Extra Rainfall Monitoring Earns Its Keep
Rainfall coverage tends to matter most in a few specific situations:
Large or elongated properties, where the distance between paddocks regularly exceeds the few kilometres over which rainfall stays reliably correlated
Properties spanning different catchments, elevations or aspects, where storm cells behave differently across the land
Regions prone to convective, thunderstorm-driven summer rainfall rather than steady, widespread frontal rain
Decisions that depend on accurate paddock-level totals, such as irrigation scheduling, grazing rotation or machinery timing after rain
You do not necessarily need a second full weather station to close this gap. A supplementary rain gauge in a paddock that regularly differs from your primary station is often enough to catch the difference, at a fraction of the cost of a second full station.
Frequently Asked Questions:
How far apart should rain gauges be on a farm?
Research on dense gauge networks suggests rainfall readings stay well correlated within roughly 1.5 to 3 kilometres, with that correlation weakening steadily beyond about 5 kilometres. On a property that spans more than a few kilometres in any direction, a single gauge is unlikely to represent the whole area during convective rainfall.
Does rainfall really vary more than wind or temperature across a property?
Yes. Wind and temperature are shaped mostly by broad weather systems and terrain, so they tend to change gradually across a property. Rainfall, especially from convective storms, can vary sharply over very short distances because it depends on where an individual storm cell forms and tracks.
What causes rainfall to vary so much over short distances?
Convective storms, the kind that produce much of Australia's summer rainfall, form from localised heating that builds an individual storm cell. That cell can be intense but narrow, so a location directly under it can record a heavy fall while a location just a few kilometres away sees little or nothing from the same system.