Average Annual Rainfall by Zip Code Map

Average annual rainfall is one of the biggest factors in whether a plant thrives on its own or needs constant watering. A plant adapted to a rainy climate can struggle in a dry one without irrigation, and a drought-adapted plant can rot where rainfall is high. This map gives you the average annual rainfall for your ZIP code so you can match plants to how much water your climate actually delivers.

How to use the map: enter your ZIP code in the search box below. The map returns the average annual rainfall for your location, in inches per year. Use that number to gauge how much supplemental watering your plants will need and to favor species suited to your natural rainfall.

Rainfall estimates on this map are calculated from a 30-year average of climate data from 1991 to 2020, which gives you a stable baseline rather than one unusually wet or dry year. Treat the number as a normal range and adjust for your microclimate: a rain shadow behind a ridge, a low spot that collects runoff, or a fast-draining sandy soil can all change how much water actually reaches your plants’ roots.

Rainfall is one climate filter. Pair it with your USDA hardiness zone, AHS heat zone, and chill hours for a fuller picture before ordering plants.

What Is Average Annual Rainfall?

Average annual rainfall is the total precipitation a location receives in a typical year, measured in inches and averaged over decades. It counts rain plus the liquid equivalent of snow. The contiguous United States averages roughly 30 inches a year, but that national figure hides an enormous range — from under 5 inches in the desert Southwest to well over 80 inches along parts of the Gulf Coast and the Pacific Northwest.

Because it is a 30-year average, the number smooths wet years and drought years into a stable planning figure. Any single year can still come in well above or below it.

Average Annual Rainfall by State

Average annual rainfall varies enormously between states — and even more within them. The driest states, such as Nevada and Arizona, average only about 10 to 14 inches a year, while the wettest in the Lower 48 — Louisiana, Mississippi, and Alabama — average close to 60 inches.

A statewide average is a rough guide at best, because rain shadow, elevation, and distance from the coast can split one state into completely different rainfall worlds. Eastern Oregon may see under 10 inches a year while the western side of the same state gets more than 80. That is exactly why a ZIP-level number beats a state average when you are choosing plants.

How to Use Rainfall When Choosing Plants

Use your average annual rainfall to judge how much water your garden gets for free, and how much you will need to add.

1. Find your rainfall. Use the map and ZIP lookup above for your average inches per year.
2. Match plant water needs to your rainfall. Drought-tolerant species like Mediterranean herbs and many natives suit low-rainfall areas; moisture-loving plants need higher rainfall or regular irrigation.
3. Plan for supplemental watering. Even in a rainy climate, new plantings need water through their first year or two while roots establish.
4. Watch distribution, not just total. A region can post a high annual total and still run a long dry summer. When the rain falls matters as much as how much.
5. Mind your soil and drainage. Sandy soil sheds rain fast; clay holds it. The same rainfall behaves very differently depending on your ground.

What Annual Rainfall Doesn’t Tell You

A single annual number can mislead on its own. Two places with the same 40-inch average can feel completely different if one spreads it evenly through the year and the other dumps it in winter and bakes through summer. The timing of rainfall — and how much heat and evaporation pull moisture back out — matters as much as the yearly total.

That is why annual rainfall is best read alongside the monthly pattern and your summer heat. It tells you the size of the bucket, not when it gets filled.

How Accurate Is a Rainfall Map?

A rainfall map is a planning estimate, not a guarantee. It is a regional average that cannot see your exact slope, your rain shadow, or the way a nearby mountain range or coastline reshapes local weather. It also cannot predict any single year — rainfall swings widely, and a drought year or a wet year can land far from the average.

For most gardeners, the map is enough to make smart plant choices and avoid the obvious mismatch — say, planting a bog-loving shrub in a 12-inch desert climate. For irrigation design or high-value plantings, compare it with a nearby weather station and your own rain gauge.

Sources and Further Reading

• NOAA 1991–2020 U.S. Climate Normals — the 30-year base data behind the rainfall averages shown on this map.
• NOAA national and state precipitation averages — context for typical U.S. annual rainfall totals.

Next step: match your rainfall to plants that fit your whole climate. Use the Plant Finder to screen by ZIP, hardiness, heat, and chill in one pass, or pair this with the USDA hardiness zone map, the AHS heat zone map, and the chill hours map.