How Accurate Are Weather Forecasts? We Measured It, Day by Day
A 5-day forecast is right about 90% of the time; a 10-day forecast, in NOAA's own words, is “only right about half the time.” We scored real forecasts against what the weather actually did — here is the full fall-off, and why where you live matters as much as how far ahead you look.
Here is the honest version, up front. A one-to-three-day forecast is reliable enough to plan around. By day five it is still useful but softening. By day seven it is a rough guide, and by day ten it is close to a coin flip. NOAA's NESDIS forecasting primer states it plainly: a five-day forecast “can accurately predict the weather approximately 90 percent of the time,” a seven-day forecast “about 80 percent,” and “a 10-day — or longer — forecast is only right about half the time.”
Those are national, round-number answers. We can do something the explainers don't: show the actual decay curve. We hold the record — 139 million NOAA observations — and we keep a running scorecard that pits past model forecasts against what each weather station went on to measure. In that verification of 14 US first-order weather stations (February 2024 through July 2026), the next-day high-temperature forecast missed by 2.9°F on average and the seven-day forecast by 5.1°F; the share of forecasts landing within 3°F of the real high fell from 62% at one day to 41% at seven. Below is the whole curve, why it bends where it does, and what “the forecast was wrong” usually really means.
The Accuracy Curve: How a Forecast Decays Each Day Out
This is our own verification set: the daily-high forecast scored against the station's observed high, averaged across 14 first-order US weather stations, 2024–2026. “Average miss” is how far off the forecast high was; “within 3°F” is how often it landed close enough that you'd call it right.
| Lead time | Average miss (daily high) | Forecasts within 3°F |
|---|---|---|
| 1-day | 2.9°F | 62% |
| 2-day | 3.2°F | 58% |
| 3-day | 3.4°F | 56% |
| 4-day | 3.7°F | 52% |
| 5-day | 4.1°F | 49% |
| 6-day | 4.6°F | 45% |
| 7-day | 5.1°F | 41% |
Notice the shape. The forecast barely degrades from day one to day three — the miss creeps from 2.9°F to 3.4°F — then the slope steepens, losing roughly half a degree of accuracy per day through the back half of the week. That is the signature of a chaotic system: skill holds, holds, then gives way.
One reconciliation worth making, because it trips people up. Our “41% within 3°F at seven days” sits next to NOAA's “about 80% accurate at seven days,” and the two aren't in conflict — they measure different things. Landing a specific city's high within 3°F is a strict test. NOAA's figure is the looser, everyday sense of “accurate”: did the forecast get the general picture right — warm or cold, wet or dry, roughly the right numbers. A forecast can be “basically right” four times out of five and still miss the exact high by four degrees. Both are true; they just answer different questions.
There Is No Single Accuracy Number — Your City Decides It
The decay curve above is a national average, and averages hide the most useful fact: a forecast is far easier in some places than others. The reason is simple once you look at how much the weather itself moves. We measured the average day-to-day swing in each city's high temperature — how different today's high is from yesterday's — across 30 years of our NOAA archive.
| City | Average day-to-day change in the high |
|---|---|
| Denver | 7.9°F |
| Boston | 6.6°F |
| Chicago | 6.2°F |
| Minneapolis | 6.1°F |
| New York City | 5.7°F |
| Dallas–Fort Worth | 5.4°F |
| Atlanta | 4.7°F |
| Seattle | 4.1°F |
| Phoenix | 3.5°F |
| Los Angeles | 3.2°F |
| Miami | 2.4°F |
Denver's high jumps an average of 7.9°F from one day to the next — a Chinook or a Front Range cold front can swing it 40° in an afternoon. Miami's moves just 2.4°F; the ocean and the tropics keep it on rails. A forecaster in Miami starts the week with an enormous head start, and it shows in the verification: Miami is the single most accurate city in our skill set, still landing within 3°F about three-quarters of the time at seven days, while the volatile Northeast cities in the same set — Boston, New York, Philadelphia — fall off to nearer 36%.
Independent work finds the same geography. When ForecastWatch scored National Weather Service high-temperature forecasts for a 2024 Washington Post analysis, it found forecasts stayed within 3°F for at least seven days out across most of Florida, five to six days across the Southwest, three to four days across the Northwest and eastern third of the country, and no more than two days across the Great Plains — the same place our data shows the weather itself swinging hardest. Accuracy isn't one number. It is a map.
Why Accuracy Falls Off a Cliff After About a Week
The limit isn't bad models or lazy forecasters. It is physics. The atmosphere is a chaotic system, which means tiny differences in its starting state grow into large differences later — the “butterfly effect” the meteorologist Edward Lorenz identified in the 1960s. We never measure today's weather perfectly everywhere, so every forecast begins with small, unavoidable errors, and those errors roughly double every few days. Early work (Charney and colleagues, 1966) pegged the doubling time near five days, which is where the familiar “about two weeks” ceiling comes from.
Push past roughly two weeks and the errors saturate: the forecast is no better than just quoting the date's long-term average. That is the real reason a 10-day app forecast feels like a guess — it is edging toward climatology, dressed up as a daily number. It is also why the serious long-range product, NOAA's Climate Prediction Center outlook, doesn't give you a date-by-date story at all. It gives you tilted odds — warmer or cooler than normal, wetter or drier — and revises them every month as the atmosphere shows its hand. For how an official temperature even becomes a record once the day arrives, see our explainer on how a weather record is verified.
What “The Forecast Was Wrong” Usually Means
Most of the time a forecast you remember as “wrong” was actually close — it just missed on timing or placement. The rain that was supposed to arrive at noon showed up at 4 p.m. The line of storms tracked 30 miles north of your town. The cold front came through a few hours early. The ingredients were forecast correctly; the fine detail wasn't, because the fine detail is the hardest part to pin down.
That is also why rain is so much harder than temperature. Temperature changes smoothly and is forecast within a few degrees for days; precipitation is patchy and binary at any one spot — it either rains on you or it doesn't. And the number people misread most is the probability of precipitation. “30% chance of rain” does not mean 30% of the day or 30% of the area will be wet — it means there is a 30% chance that measurable rain falls at any given point in the forecast area. A 30% day that stays dry where you are standing is a correct forecast, not a busted one.
Common Questions
How far out are weather forecasts accurate?
Roughly a week. NOAA puts a 5-day forecast at about 90% accurate and a 7-day at about 80%; a 10-day forecast, in NOAA’s words, is “only right about half the time.” The hard ceiling is around two weeks — beyond that, tiny errors in today’s measurements grow until a forecast is no better than simply quoting the season’s average.
Why are 10-day forecasts so often wrong?
The atmosphere is chaotic: small, unavoidable errors in the starting conditions double roughly every few days, so by day 10 they have swamped the signal. That is the butterfly effect Edward Lorenz described in the 1960s. A 10-day forecast is best read as a tendency — warmer or cooler than normal — not a promise about a specific day.
Is the weather app or the local TV forecast more accurate?
For the first few days there is little difference — most apps and TV stations run the same underlying government and European models. Differences show up at longer leads and in tricky terrain, where a human forecaster who knows the local microclimate can beat a raw app feed. The bigger accuracy driver is where you live, not which source you check.
Which is harder to forecast, temperature or rain?
Rain. Temperature trends on a smooth curve and is forecast within a few degrees several days out. Precipitation is patchy and timing-sensitive — a storm an hour late or 20 miles off still “happened,” just not where or when the forecast implied. That mismatch is why a forecast can feel wrong even when it was broadly right.
How to Read a Forecast Like a Forecaster
- Trust the next three days. Inside 72 hours the forecast high is typically within about 3°F and the rain timing is usually right. Plan around it.
- Treat days 5–7 as a sketch. Use them for direction — warming up, a front coming — not for a cookout time. Re-check daily; the forecast you see tomorrow for Saturday is better than today's.
- Read day 8–10 as a tendency, nothing more. “A bit warmer than normal” is about all those numbers can honestly tell you.
- Factor in where you are. A 7-day forecast in Miami or coastal California is worth far more than the same forecast in Denver or across the Plains.
- Watch the probability, not the icon. A 30% rain chance that stayed dry on you did its job. For the big seasonal picture, use NOAA's probabilistic outlook over any almanac — see how those stack up in our look at whether the Farmers' Almanac is accurate and how accurate Punxsutawney Phil really is.
Want to see the forecast score for your own city, lead by lead? We publish the full per-station ranking on our forecast-predictability page. And if you'd rather skip the guessing entirely — we can't tell you what day 10 holds, but we can tell you exactly what the weather did on any day since 1970. Look up a past date for any US city and compare it to whatever the forecast promised.