FMI Open Data for Home Assistant

A Home Assistant integration for the Finnish Meteorological Institute's open data. Observations and forecasts from FMI's stations, a weather forecast for any place, and FMI's weather warnings.

The data in the picture is made up.

What is it?

FMI publishes almost everything it measures as open data. That is the weather at some 200 stations, rain, snow depth, sea level, waves, water temperature, air quality, solar radiation and STUK's radiation measurements, along with FMI's forecasts and weather warnings. The weather integrations usually give you the temperature and the forecast. This one gives you the rest as well.

You add stations and places to it. A station is one of FMI's stations, with the measurements you want from it, each a sensor. You start from what you want to measure, such as precipitation, and the integration offers the stations that measure it, nearest first. A place is a point on a map with FMI's weather forecast for it, the weather warnings in force there, or both. Each station and place is a device in Home Assistant, so it can be put in an area.

For a one-off chart or a script, an action reads any station's observations over a time range without a sensor.

No account or API key is needed. FMI's open data service is used anonymously.

Installation

With HACS

1. Add this repository to HACS custom repositories with type Integration
2. Search for FMI Open Data in HACS and download it
3. Restart Home Assistant
4. Add FMI Open Data in Settings › Devices & services

Manual

1. Download the source code from the latest release
2. Copy the custom_components/fmi_open_data folder to your Home Assistant installation's config/custom_components folder
3. Restart Home Assistant
4. Add FMI Open Data in Settings › Devices & services

Settings

Adding the integration asks for a language, English or Finnish. FMI's names of queries and parameters, the names of the measurements it suggests, and the warning texts are in that language. Change it later with Reconfigure.

Name	Type	Description	Default
Language	enum	The language of FMI's names and texts	Home Assistant's, else English

Options

Configure on the integration sets when a measurement's data counts as stale. The settings apply to every measurement.

Name	Type	Description	Default
Raise a repair issue	bool	Tell you with a repair issue when a measurement stops getting data	true
Hours without new data	int	How old the newest data may be before it counts as stale	24

Daily, monthly and yearly statistics are published only once the day, month or year is over, so for those the limit is never shorter than three days, two months or two years.

Adding measurements

Choose Add measurements on the integration page.

1. What to measure. Every parameter of FMI's station queries is in one list, about 380 of them, with the query each comes from. Search by name, such as rain or snow, and pick as many as you like.
2. A station for each. The stations that have reported the parameter recently, nearest to your home first, with their distance. The station you chose for the previous parameter is suggested when it has this one too. Switch on Show all of the query's stations for the ones that have not reported it lately. A parameter nobody has reported lately, such as wave height while the buoys are ashore for the winter, starts from all of them.
   • A model forecast, such as Harmonie or MEPS, is for any point. Pick it on a map and give the place a name.
   • STUK's air radioactivity is measured by place, not by station. Type the place's name, such as Kotka.
3. Names. Filled in from FMI's description of the parameter, with the period of a daily or hourly query, such as "Sademäärä, tunti". Home Assistant shows the station's name in front of it, so the sensor reads "Lappeenranta lentoasema Sademäärä, tunti".

A measurement at a station that is already there is added to it. A new station becomes a new device. One run can add measurements to several stations.

Changing a station

Reconfigure on a station opens a menu:

• Add measurements: only what the station has reported is offered.

• Change a measurement's settings:

  Name	Type	Description	Default
  Unit	string	The unit to show. Empty uses FMI's own, which FMI does not give for every parameter	FMI's
  Report -1 as 0	bool	For parameters that use -1 for no measurable value, such as daily precipitation	false
  Forecast hours	int	How many hours ahead a forecast shows	36
  Forecast past hours	int	How many hours of the forecast already past it keeps	5
  Forecast step	int	Minutes between two forecast values	30

  The forecast settings are only for forecasts.

• Remove measurements: a station keeps at least one. To remove it altogether, delete it on the integration page.

The station itself does not change, because a different station is a different device. To rename a measurement, rename its sensor in Home Assistant.

Adding a place

Choose Add place on the integration page.

Name	Type	Description	Default
Place	location	The point, and a radius around it for the warnings	Home, 1 km
Name	string	The place's name, shown in front of its entities' names	Home Assistant's location name
Weather forecast	bool	A weather entity with FMI's forecast for the place	true
Warning types	list	The warnings to follow. Empty follows none	All

A place follows the forecast, the warnings or both. A warning is included when one of its areas covers the place or comes within the radius. The areas are municipalities for warnings on land and sea areas for warnings at sea, and a sea area includes its islands. On the shore, a radius of a kilometre or two brings in the nearby sea area.

Reconfigure on a place changes any of these. Switching the forecast or the warnings off removes their entities.

Sensors

Every measurement is a sensor, named after the station and the measurement. An observation's state is the latest value, a forecast's the next one.

Attribute	Description
latitude, longitude	Where the station is
label	The measurement's name
language	The language of FMI's texts
query_id	FMI's query, such as fmi::observations::weather::hourly::simple
parameter	FMI's parameter, such as PRA_PT1H_ACC
location_type, location_id	How the station is identified (fmisid, geoid, place or latlon), and the value
no_data_issue, no_data_issue_hours	The stale data settings that apply, the hours after the minimum for the query
time, value	An observation's time and value
forecast	A forecast's values, each with time and value
forecast_hours, forecast_past_hours, forecast_step	A forecast's settings

Stale data

Every measurement also has a diagnostic binary sensor, such as binary_sensor.lappeenranta_lentoasema_sademaara_tunti_stale_data. It is on while the newest data FMI holds for the measurement is older than the limit in the options, and it turns off by itself when data comes back. The age comes from FMI's own timestamps, so restarting Home Assistant does not reset it.

FMI removes parameters from stations, and stations are now and then shut down or renumbered. Neither is an error: the query just returns nothing. A repair issue then tells you whether the station returns nothing at all, or still reports but no longer has your parameter, and lists what it does have. Remove the measurement and add a working one, and the issue clears.

Weather

A place with the forecast on has a weather entity named after the place. It shows the hour under way, and Home Assistant's weather cards and voice assistants can use its forecasts:

• Hourly for about nine days, as far as FMI's forecast reaches
• Daily, a day being the local calendar day
• Twice daily, from 6 to 18 and from 18 to 6

A day or a half takes its condition and wind from one hour, 14:00 for a day and a daytime half and 02:00 for a night. Its temperature is the highest and lowest, its precipitation the sum and its precipitation probability and gust the highest. The forecast is FMI's edited one, the same that FMI's own site shows, read every 30 minutes. When FMI cannot be reached, the last forecast is kept for three hours.

Warnings

Warning level

A place with warnings has a sensor for the highest warning level in force now, none, yellow, orange or red.

Attribute	Description
label	The place's name
language	The language of the warning texts
latitude, longitude, radius	The place and the radius in metres
warning_types	The warning types followed
active_warnings	The number of warnings in force now
warnings	Every warning that concerns the place, in force or coming up, earliest first

Only the level is kept in history, not the warnings attribute.

Each warning, in warnings and in the events below, has these fields:

Field	Description
id	FMI's identifier for this version of the warning
type	The warning type, such as seaWind or seaWaveHeight
level	yellow, orange or red
event	The warning's name, such as Tuulivaroitus merelle
severity	Moderate, Severe or Extreme
onset, expires	When the warning comes into force and when it ends
headline, description	FMI's texts
impacts	The typical impacts, such as Mahdollisesti vaarallinen huviveneille.
probability	The probability in percent, when FMI gives one
areas	The warning's areas that concern the place
parameters	The warning type's values, such as windIntensity: 14, windIntensityUom: m/s and windDirection: 180

The warning types are wind on land and at sea, thunderstorms on land and at sea, heavy rain, traffic weather, pedestrian weather, forest fire weather, heat, cold, UV, wave height, sea level and ice accretion.

Warning events

The place's event entity fires when something happens to a warning that concerns it:

Event type	When
issued	A new warning concerns the place
updated	A warning's level, validity, texts or values changed
cancelled	A warning was withdrawn before it expired

The event data is the warning, with the fields above. FMI republishes its warnings regularly, and one republished without changes fires nothing. A warning coming into force or running out changes the level instead, and the warnings already in force when Home Assistant starts fire nothing.

Actions

fmi_open_data.get_observations

One station's observations over a time range, straight from FMI, without a sensor for each value. It returns the station's name and coordinates and one row per time.

Field	Description	Default
Query	An FMI observation query, such as fmi::observations::weather::hourly
Station	The station's FMISID
Parameters	The query's parameters, such as TA_PT1H_AVG
Start	The start of the time range	24 hours before the end
End	The end of the time range	Now
Step	Minutes between values	The query's own

FMI limits how long a range one request may cover, differently for each query. It is a week for the 10-minute observations, a month for the hourly ones and a year for the daily ones. A longer range is refused with FMI's own reason, which tells the limit. A range with nothing in it returns an empty list.

Examples

The sea level, measured and forecast

The water level at a mareograph with FMI's forecast for the same place, in apexcharts-card. Add the mareograph's water level and the sea level forecast from the nearest forecast point as measurements, and give them their units (FMI gives none): millimetres for the observation and centimetres for the forecast.

type: custom:apexcharts-card
graph_span: 4d
span:
  offset: +2d
now:
  show: true
header:
  show: true
  title: Sea level
series:
  - entity: sensor.hanko_pikku_kolalahti_wlevn2k_pt1s_instant
    name: Measured
    transform: return x / 10
    unit: cm
    extend_to: now
  - entity: sensor.hanko_sealeveln2000
    name: Forecast
    data_generator: |
      return entity.attributes.forecast.map((entry) => [new Date(entry.time).getTime(), entry.value]);

The warnings on a dashboard

Every warning that concerns a place, in Home Assistant's own markdown card. The warnings in force come first in the list, so the first active_warnings of them are the ones in force now.

type: markdown
title: Weather warnings
content: |
  {% set warnings = state_attr('sensor.cabin_warning_level', 'warnings') or [] %}
  {% set active = state_attr('sensor.cabin_warning_level', 'active_warnings') or 0 %}
  {% for w in warnings %}
  <ha-alert alert-type="{{ 'error' if w.level == 'red' else 'warning' }}" title="{{ w.event }}">
  <b>{{ 'In force now.' if loop.index <= active else 'Coming.' }}</b> {{ w.description }} {{ w.impacts }}<br>
  <i>{{ as_timestamp(w.onset) | timestamp_custom('%a %H:%M') }} – {{ as_timestamp(w.expires) | timestamp_custom('%a %H:%M') }}</i>
  </ha-alert>
  {% else %}
  <ha-alert alert-type="success">No warnings</ha-alert>
  {% endfor %}

A notification when a warning is issued

triggers:
  - trigger: state
    entity_id: event.cabin_warning
    not_from: unavailable
conditions:
  - condition: state
    entity_id: event.cabin_warning
    attribute: event_type
    state: issued
actions:
  - action: notify.mobile_app_phone
    data:
      title: "{{ trigger.to_state.attributes.headline }}"
      message: "{{ trigger.to_state.attributes.description }}"

The past week's daily precipitation

action: fmi_open_data.get_observations
data:
  query: fmi::observations::weather::daily
  station: 101124
  parameters:
    - rrday
  start: "{{ now() - timedelta(days=7) }}"
response_variable: rain

Upgrading from 3.x

Version 4.0.0 is a big change, and the names of all the entities change with it.

The domain is now fmi_open_data instead of fmi, which another integration also uses. After updating, add FMI Open Data once in Settings › Devices & services and choose to move the existing setup. Its sensors and warnings places move to the new integration, and Home Assistant then asks you to delete the old custom_components/fmi folder, which HACS leaves behind.

Sensors become stations and places. On the first start, the sensors are merged into stations by the station they read, and the warnings places into places by their coordinates. Two warnings places at the same point are merged with all the warning types either followed and the larger radius.

The names change. Home Assistant puts a device's name in front of its entities' names, so each measurement is renamed after what it measures, from FMI's description of the parameter, and the station's name comes in front. A place keeps the name it had, and its level sensor and event are called the warning level and the warning. Rename anything you like in Home Assistant afterwards.

What stays: entity IDs, and with them history, long-term statistics, dashboards and automations. Disabled entities stay disabled.

Units: FMI's metadata has no unit for some parameters, such as the water level and STUK's air radioactivity. Give them one in the measurement's settings. Home Assistant may then ask under Developer tools › Statistics what to do with the statistics recorded without a unit. Keep them under the new unit, as the numbers are the same.

The query_name attribute is gone.

Data

The data comes from FMI's open data service under the Creative Commons Attribution 4.0 licence, which also covers the Radiation and Nuclear Safety Authority STUK's radiation data and the air quality data published there. Every entity credits FMI in its attribution.

• Measurements are read from FMI's WFS service every five minutes each.
• The weather forecast is FMI's edited point forecast, read every 30 minutes a place.
• The warnings are FMI's CAP warning feed, read every ten minutes and shared by every place.
• Adding measurements reads every station query once over Finland to see which stations report what, about 40 requests, kept for an hour.

Translating

The texts are in custom_components/fmi_open_data/translations/, one JSON file per language, such as en.json and fi.json. To add a language, copy en.json to the new language's code and translate the values. FMI's own names of queries, parameters and warnings come from FMI in English or Finnish.

Development

Requires Python 3.14.

python3.14 -m venv .venv
.venv/bin/pip install -r requirements_test.txt
.venv/bin/pytest
.venv/bin/ruff check .

The tests run on made-up data and trimmed real responses from FMI's public stations, without network access.

Path	What it contains
__init__.py	Setup
config_flow.py	The language, the options, adding and changing stations and places
catalogue.py	What can be measured, and which stations report what
structure.py	Stations and places, their devices, and the move from 3.x's subentries
migration.py	The move from the old fmi domain
session.py	FMI's WFS service
query_coordinator.py	Reading a measurement, and noticing stale data
weather_coordinator.py	The point forecast, and its days and halves
warning_coordinator.py, cap.py	The warning feed and the warnings for a place
sensor.py, binary_sensor.py, event.py, weather.py	The entities
services.py	The get_observations action
diagnostics.py	The diagnostics download, with places left out
translations/<language>.json	Home Assistant UI texts

Support

Hey dude! Help me out for a couple of 🍻 or a ☕!

License

MIT. The data is FMI's, under CC BY 4.0.