Frost Risks

A modern Home Assistant custom component for comprehensive frost risk monitoring and meteorological calculations.

Features

This integration creates 8 advanced meteorological sensors based on temperature and humidity readings:

1. Absolute Humidity (g/m³) - Actual water vapor content in the air
2. Dew Point (°C) - Temperature at which water vapor condenses
3. Frost Point (°C) - Temperature at which frost forms (below 0°C)
4. Freezing Point (°C) - Atmospheric freezing point with humidity effects
5. Wet-Bulb Temperature (°C) - Temperature with evaporative cooling
6. Vapor Pressure (hPa) - Partial pressure of water vapor
7. Humidity Ratio (kg/kg) - Mass of water vapor per unit mass of dry air
8. Frost Risk Level (0-5) - Multi-factor frost risk assessment

Device grouping

The integration creates a device per config entry (identifier: (frost_risks, entry_id)). All generated sensors for that instance are attached to that device, which makes them easier to find and manage in Settings → Devices & Services.

Modern Architecture

• ✅ Config Flow UI - Easy setup through Home Assistant UI (no YAML required)
• ✅ SensorEntity - Uses modern Home Assistant sensor architecture
• ✅ Async/Await - Fully asynchronous implementation
• ✅ Auto-Update - Automatically recalculates when temperature or humidity changes
• ✅ HACS Compatible - Ready for installation via HACS
• ✅ Bilingual - English and Dutch translations included

Accurate Meteorological Formulas

All calculations use scientifically validated formulas:

• Magnus-Tetens formula for dew point
• Stull's formula (2011) for wet-bulb temperature
• ASHRAE standards for humidity ratio
• Modified Magnus formula for frost point

Installation

HACS (Recommended)

1. Open HACS in Home Assistant
2. Go to "Integrations"
3. Click the three dots in the top right corner
4. Select "Custom repositories"
5. Add https://github.com/Patrick1610/home-assistant-frost-risks as repository
6. Category: Integration
7. Click "Add"
8. Search for "Frost Risks" and install
9. Restart Home Assistant

Manual Installation

1. Copy the custom_components/frost_risks folder to your Home Assistant's custom_components directory
2. Restart Home Assistant

Configuration

UI Configuration (Recommended)

1. Go to Settings → Devices & Services
2. Click + Add Integration
3. Search for Frost Risks
4. Enter a name for your sensor group
5. Select your temperature sensor (must have device_class: temperature)
6. Select your humidity sensor (must have device_class: humidity)
7. Click Submit

The integration will automatically create all 8 sensors.

Example Sensors Created

If you name your integration "Living Room", you'll get:

sensor.living_room_absolute_humidity
sensor.living_room_dew_point
sensor.living_room_frost_point
sensor.living_room_freezing_point
sensor.living_room_wet_bulb_temperature
sensor.living_room_vapor_pressure
sensor.living_room_humidity_ratio
sensor.living_room_frost_risk_level

Frost Risk Levels

The frost risk level sensor provides a 0-5 scale based on multiple meteorological factors:

Level	Description	Risk
0	No Risk	No frost expected
1	Very Low	Minimal frost risk
2	Low	Slight possibility of frost
3	Moderate	Frost possible in favorable conditions
4	High	Frost likely
5	Very High	Frost highly likely

The risk assessment considers:

• Current temperature
• Dew point temperature
• Wet-bulb temperature
• Freezing point
• Absolute humidity

Usage Examples

Automation - Frost Warning

automation:
  - alias: "Frost Warning"
    trigger:
      - platform: numeric_state
        entity_id: sensor.outdoor_frost_risk_level
        above: 3
    action:
      - service: notify.mobile_app
        data:
          title: "⚠️ Frost Warning"
          message: "High frost risk detected. Protect sensitive plants!"

Automation - Smart Heating

automation:
  - alias: "Prevent Pipe Freezing"
    trigger:
      - platform: numeric_state
        entity_id: sensor.garage_frost_risk_level
        above: 4
    action:
      - service: climate.set_temperature
        target:
          entity_id: climate.garage_heater
        data:
          temperature: 5

Dashboard Card

type: entities
title: Frost Monitoring
entities:
  - entity: sensor.outdoor_temperature
  - entity: sensor.outdoor_humidity
  - entity: sensor.outdoor_dew_point
  - entity: sensor.outdoor_frost_point
  - entity: sensor.outdoor_wet_bulb_temperature
  - entity: sensor.outdoor_frost_risk_level

Sensor Attributes

Each sensor includes additional attributes:

temperature: 2.5  # Source temperature in °C
humidity: 85      # Source humidity in %

The frost risk level sensor also includes:

description_en: "High"       # English description
description_nl: "Hoog"       # Dutch description

Technical Details

Formulas Used

Absolute Humidity

AH = (6.112 × e^((17.67×T)/(T+243.5)) × RH × 2.1674) / (273.15 + T)

Dew Point (Magnus-Tetens)

α = (17.27×T)/(237.7+T) + ln(RH/100)
Td = (237.7 × α) / (17.27 - α)

Wet-Bulb Temperature (Stull's Formula)

Tw = T×atan(0.151977×√(RH+8.313659)) + atan(T+RH) - atan(RH-1.676331)
     + 0.00391838×RH^1.5×atan(0.023101×RH) - 4.686035

Vapor Pressure

es = 6.112 × exp((17.67×T)/(T+243.5))
e = es × (RH/100)

Humidity Ratio

W = 0.622 × (e / (P - e))
where P = 1013.25 hPa (standard atmospheric pressure)

Multiple Instances

You can add multiple instances of this integration for different locations:

1. Outdoor monitoring (garden, balcony)
2. Indoor monitoring (living room, bedroom)
3. Garage/Shed monitoring
4. Greenhouse monitoring

Each instance creates its own set of 8 sensors.

Support & Contributing

• 🐛 Issues: Report bugs or request features
• 💬 Discussions: Ask questions and share ideas
• 🔧 Pull Requests: Contributions are welcome!

Credits

Originally inspired by papo-o/home-assistant-frost-risks, completely rewritten for modern Home Assistant architecture.

License

MIT License - See LICENSE file for details