About the data: Budapest weather
29 October 2026
The banner and the data slides follow Budapest's weather through a working pipeline. This page explains where each number comes from, why, and how the two sources are combined.
Two sources, two roles
Open-Meteo is the primary source. It serves weather-model data: the forecast, the recent days, what earlier forecasts said, and ERA5, a reconstruction of the weather back to 1940. Past, present and future come from models with consistent definitions and no gaps, so every slide compares like with like: today against the same date in 86 years, a forecast against what followed. Model values describe a grid cell over the city centre; they are estimates, not readings.
HungaroMet, the Hungarian meteorological service, adds measurements: the 10-minute readings of its Budapest Pestszentlőrinc station (44527). They are what actually happened, but at one point 13 km south-east of the centre, with occasional gaps, only since collection began, and without the weather code or cloud cover a model gives. So the station is reported alongside the model and used to check it, not to replace it.
One station supplies every measured value, so each number has a single lineage. Pestszentlőrinc is the Budapest station that measures visibility and sunshine as well as temperature and rain.
The banner
The dots follow Open-Meteo's current weather: temperature, wind and the sky. Models can get the sky wrong, and low cloud with drizzle is a common miss in a Budapest autumn, so the sky is checked against the station's last 30 minutes. The first rule that applies decides:
| When | The sky shown |
|---|---|
| The station's reading is missing or over 40 minutes old | the model's |
| The model has a thunderstorm | the model's: a station cannot see lightning |
| At least 0.1 mm of rain or snow fell | the model's type if it has precipitation too; otherwise drizzle, rain or snow from the measured intensity and temperature |
| Nothing fell, but the model has precipitation | the cloud measured from sunshine, or overcast at night |
| Visibility under 1 km | fog (and the model's fog is dropped when visibility is 5 km or more) |
| Daylight | clear to overcast, from the sunshine measured against a cloudless sky at that sun height |
| Otherwise (night, dry, no fog) | the model's |
The line at the foot of the banner gives the model's temperature with the station's in brackets, and marks a sky the station decided as measured. Limits: very light drizzle can fall below the rain gauge's smallest step (0.1 mm) and go unmeasured, and a shower over the centre can miss a station 13 km away.
Slide by slide
| Slide | What it shows | Source |
|---|---|---|
| 1 Ingestion | how data arrives | illustration |
| 2 Storage, 3 Validation | rows being stored and checked | simulated |
| 4 Transformation | hourly temperatures for the last 14 complete days, rolled up into daily highs | Open-Meteo |
| 5 BI | the high on today's date in every year since 1940, the normal, and today | ERA5 for every past year; today from Open-Meteo, live |
| 6 ML | 30 days of daily highs, the week's forecast, what was forecast the day before and how far off it was | Open-Meteo, with the station's measured highs alongside and the error against both |
| 7 AI | this month's highs against normal | Open-Meteo |
| 8 Governance | how the data is governed | illustration |
Slide 5 and the shaded error band on slide 6 stay on the model because both need many years from one source. The station's readings are collected from 29 October 2026; earlier days were filled in only for the 30 days the slides show.
Definitions
Days are Budapest calendar days in local time, including the days the clocks change (23 or 25 hours).
Hourly temperature: the value at the full hour; for the station, its reading at that minute.
Daily high: the highest of the day's hourly temperatures, for the model and the station alike. A station day counts only when every hour was measured.
Normal: the 1991–2020 average high for each calendar day, from ERA5, smoothed over 31 days.
Forecast error: how far the forecast made the day before was from the day's high, on average and ignoring the sign, over the last 14 complete days.
Updates and checks
Live: the banner and today's figures come from this site's own server, refreshed every 5 minutes. Your browser contacts neither source.
Daily, just after midnight: a scheduled job fetches both sources, checks that every expected day and hour is there and that values are possible for Budapest, recalculates the slides and publishes them. If Open-Meteo fails a check, nothing is published and the site keeps the previous day's data. If the station cannot be read, its figures are left empty and the rest is published.
Everything collected is kept, so each published number can be traced back to the rows it came from.
Sources and licences
Open-Meteo, open-meteo.com, licensed CC BY 4.0.
ERA5: Copernicus Climate Change Service, through Open-Meteo.
Database: Meteorological Database, HungaroMet Nonprofit Zrt., odp.met.hu. Derived values: hourly readings, daily highs and the banner's sky.
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