fix: honor Explain Weather unit preferences

CHANGELOG.md

@@ -31,6 +31,7 @@ All notable changes to this project will be documented in this file.
 - The tray text format dialog now warns you about unknown placeholders or unbalanced braces before saving, so a typo like `{tmp}` can't quietly end up in your tray tooltip.
 - Closing the Add or Edit Location dialog while a search or current-location detection is still running no longer risks a crash.
 - Weather history's "Today vs Yesterday" section now reads naturally when both days have the same temperature, instead of "is 0.0°F about the same than yesterday".
+- Explain Weather now uses your effective unit preference, including automatic location-based units like Canadian kPa, instead of always prompting the AI with imperial current-condition values.
 
 ## [0.7.2] - 2026-05-30
 

src/accessiweather/ai_explainer_models.py

@@ -83,6 +83,13 @@ class WeatherContext:
     pressure: float | None
     alerts: list[dict[str, Any]]
     forecast_summary: str | None = None
+    temperature_text: str | None = None
+    wind_speed_unit: str | None = None
+    wind_text: str | None = None
+    visibility_unit: str | None = None
+    visibility_text: str | None = None
+    pressure_unit: str | None = None
+    pressure_text: str | None = None
     local_time: str | None = None
     utc_time: str | None = None
     timezone: str | None = None
@@ -100,7 +107,9 @@ def to_prompt_text(self) -> str:
         if self.time_of_day:
             parts.append(f"Time of Day: {self.time_of_day}")
 
-        if self.temperature is not None:
+        if self.temperature_text:
+            parts.append(f"Temperature: {self.temperature_text}")
+        elif self.temperature is not None:
             parts.append(f"Temperature: {self.temperature}°{self.temperature_unit}")
 
         if self.conditions:
@@ -109,17 +118,29 @@ def to_prompt_text(self) -> str:
         if self.humidity is not None:
             parts.append(f"Humidity: {self.humidity}%")
 
-        if self.wind_speed is not None:
-            wind_info = f"Wind: {self.wind_speed} mph"
+        if self.wind_text:
+            wind_info = f"Wind: {self.wind_text}"
+            if self.wind_direction:
+                wind_info += f" from {self.wind_direction}"
+            parts.append(wind_info)
+        elif self.wind_speed is not None:
+            wind_unit = self.wind_speed_unit or "mph"
+            wind_info = f"Wind: {self.wind_speed} {wind_unit}"
             if self.wind_direction:
                 wind_info += f" from {self.wind_direction}"
             parts.append(wind_info)
 
-        if self.visibility is not None:
-            parts.append(f"Visibility: {self.visibility} miles")
-
-        if self.pressure is not None:
-            parts.append(f"Pressure: {self.pressure} inHg")
+        if self.visibility_text:
+            parts.append(f"Visibility: {self.visibility_text}")
+        elif self.visibility is not None:
+            visibility_unit = self.visibility_unit or "miles"
+            parts.append(f"Visibility: {self.visibility} {visibility_unit}")
+
+        if self.pressure_text:
+            parts.append(f"Pressure: {self.pressure_text}")
+        elif self.pressure is not None:
+            pressure_unit = self.pressure_unit or "inHg"
+            parts.append(f"Pressure: {self.pressure} {pressure_unit}")
 
         if self.alerts:
             alert_texts = []

src/accessiweather/ai_explainer_prompting.py

@@ -170,6 +170,13 @@ def _build_prompt(
             pressure=weather_data.get("pressure"),
             alerts=weather_data.get("alerts", []),
             forecast_summary=weather_data.get("forecast_summary"),
+            temperature_text=weather_data.get("temperature_text"),
+            wind_speed_unit=weather_data.get("wind_speed_unit"),
+            wind_text=weather_data.get("wind_text"),
+            visibility_unit=weather_data.get("visibility_unit"),
+            visibility_text=weather_data.get("visibility_text"),
+            pressure_unit=weather_data.get("pressure_unit"),
+            pressure_text=weather_data.get("pressure_text"),
             local_time=weather_data.get("local_time"),
             utc_time=weather_data.get("utc_time"),
             timezone=weather_data.get("timezone"),
@@ -258,7 +265,11 @@ def _generate_cache_key(self, weather_data: dict[str, Any], location_name: str)
         key_parts = [
             f"loc:{location_name}",
             f"temp:{weather_data.get('temperature')}",
+            f"temp_text:{weather_data.get('temperature_text')}",
             f"cond:{weather_data.get('conditions')}",
+            f"wind:{weather_data.get('wind_text') or weather_data.get('wind_speed')}",
+            f"visibility:{weather_data.get('visibility_text') or weather_data.get('visibility')}",
+            f"pressure:{weather_data.get('pressure_text') or weather_data.get('pressure')}",
             f"model:{self.get_effective_model()}",
         ]
         return "ai_explanation:" + ":".join(key_parts)

src/accessiweather/ui/dialogs/explanation_dialog.py

@@ -174,7 +174,13 @@ def _do_regenerate():
                     wx.CallAfter(self._on_regenerate_error, "No weather data available.")
                     return
 
-                weather_dict = build_current_weather_payload(weather_data)
+                weather_dict = build_current_weather_payload(
+                    weather_data,
+                    temperature_unit_preference=getattr(settings, "temperature_unit", "both"),
+                    location=location,
+                )
+                if location:
+                    add_location_time_context(weather_dict, location)
 
                 loop = asyncio.new_event_loop()
                 try:
@@ -382,7 +388,11 @@ def generate_explanation():
             )
 
             # Build weather data dict from current conditions
-            weather_dict = build_current_weather_payload(weather_data)
+            weather_dict = build_current_weather_payload(
+                weather_data,
+                temperature_unit_preference=getattr(settings, "temperature_unit", "both"),
+                location=location,
+            )
 
             # Add local time info for the location
             add_location_time_context(weather_dict, location)

src/accessiweather/ui/dialogs/explanation_generation.py

@@ -8,6 +8,9 @@
 from zoneinfo import ZoneInfo
 
 from ...ai_explainer import ExplanationStyle
+from ...units import resolve_display_unit_system, resolve_temperature_unit_preference
+from ...utils.temperature_utils import TemperatureUnit, format_temperature
+from ...utils.unit_utils import format_pressure, format_visibility, format_wind_speed
 
 logger = logging.getLogger(__name__)
 
@@ -29,18 +32,61 @@ def resolve_explanation_style(settings: Any) -> ExplanationStyle:
     return style_map.get(settings.ai_explanation_style, ExplanationStyle.STANDARD)
 
 
-def build_current_weather_payload(weather_data: Any) -> dict[str, Any]:
+def build_current_weather_payload(
+    weather_data: Any,
+    *,
+    temperature_unit_preference: str | None = "both",
+    location: Any | None = None,
+) -> dict[str, Any]:
     """Build the AI explainer payload from current app weather data."""
     current = weather_data.current
+    unit_pref = resolve_temperature_unit_preference(temperature_unit_preference, location)
+    unit_system = resolve_display_unit_system(temperature_unit_preference, location)
+
+    temperature, temperature_unit = _resolve_temperature_for_prompt(current, unit_pref)
     weather_dict: dict[str, Any] = {
-        "temperature": current.temperature_f,
-        "temperature_unit": "F",
+        "temperature": temperature,
+        "temperature_unit": temperature_unit,
+        "temperature_text": _formatted_or_none(
+            format_temperature(
+                current.temperature_f,
+                unit=unit_pref,
+                temperature_c=current.temperature_c,
+            )
+        ),
         "conditions": current.condition,
         "humidity": current.humidity,
-        "wind_speed": current.wind_speed_mph,
+        "wind_speed": _resolve_wind_speed_for_prompt(current, unit_pref, unit_system),
+        "wind_speed_unit": _resolve_wind_speed_unit_label(unit_pref, unit_system),
+        "wind_text": _formatted_or_none(
+            format_wind_speed(
+                current.wind_speed_mph,
+                unit=unit_pref,
+                wind_speed_kph=current.wind_speed_kph,
+                unit_system=unit_system,
+            )
+        ),
         "wind_direction": current.wind_direction,
-        "visibility": current.visibility_miles,
-        "pressure": current.pressure_in,
+        "visibility": _resolve_visibility_for_prompt(current, unit_pref, unit_system),
+        "visibility_unit": _resolve_visibility_unit_label(unit_pref, unit_system),
+        "visibility_text": _formatted_or_none(
+            format_visibility(
+                current.visibility_miles,
+                unit=unit_pref,
+                visibility_km=current.visibility_km,
+                unit_system=unit_system,
+            )
+        ),
+        "pressure": _resolve_pressure_for_prompt(current, unit_pref, unit_system),
+        "pressure_unit": _resolve_pressure_unit_label(unit_pref, unit_system),
+        "pressure_text": _formatted_or_none(
+            format_pressure(
+                current.pressure_in,
+                unit=unit_pref,
+                pressure_mb=current.pressure_mb,
+                unit_system=unit_system,
+            )
+        ),
         "alerts": [],
         "forecast_periods": [],
     }
@@ -67,6 +113,133 @@ def build_current_weather_payload(weather_data: Any) -> dict[str, Any]:
     return weather_dict
 
 
+def _formatted_or_none(value: str) -> str | None:
+    return None if value == "N/A" else value
+
+
+def _resolve_temperature_for_prompt(
+    current: Any, unit_pref: TemperatureUnit
+) -> tuple[float | None, str]:
+    if current.temperature_f is None and current.temperature_c is not None:
+        temperature_f = (current.temperature_c * 9 / 5) + 32
+    else:
+        temperature_f = current.temperature_f
+
+    if current.temperature_c is None and current.temperature_f is not None:
+        temperature_c = (current.temperature_f - 32) * 5 / 9
+    else:
+        temperature_c = current.temperature_c
+
+    if unit_pref == TemperatureUnit.CELSIUS:
+        return temperature_c, "C"
+    if unit_pref == TemperatureUnit.BOTH:
+        return temperature_f, "F"
+    return temperature_f, "F"
+
+
+def _resolve_wind_speed_for_prompt(
+    current: Any, unit_pref: TemperatureUnit, unit_system: Any | None
+) -> float | None:
+    wind_speed_mph = current.wind_speed_mph
+    wind_speed_kph = current.wind_speed_kph
+    if wind_speed_mph is None and wind_speed_kph is not None:
+        wind_speed_mph = wind_speed_kph * 0.621371
+    elif wind_speed_kph is None and wind_speed_mph is not None:
+        wind_speed_kph = wind_speed_mph * 1.60934
+
+    normalized_system = getattr(unit_system, "value", unit_system)
+    if normalized_system == "ca":
+        return wind_speed_kph
+    if normalized_system == "si":
+        return wind_speed_kph / 3.6 if wind_speed_kph is not None else None
+    if normalized_system in {"us", "uk"}:
+        return wind_speed_mph
+    if unit_pref == TemperatureUnit.CELSIUS:
+        return wind_speed_kph
+    return wind_speed_mph
+
+
+def _resolve_wind_speed_unit_label(unit_pref: TemperatureUnit, unit_system: Any | None) -> str:
+    normalized_system = getattr(unit_system, "value", unit_system)
+    if normalized_system in {"us", "uk"}:
+        return "mph"
+    if normalized_system == "ca":
+        return "km/h"
+    if normalized_system == "si":
+        return "m/s"
+    if unit_pref == TemperatureUnit.CELSIUS:
+        return "km/h"
+    if unit_pref == TemperatureUnit.BOTH:
+        return "mph (km/h)"
+    return "mph"
+
+
+def _resolve_visibility_for_prompt(
+    current: Any, unit_pref: TemperatureUnit, unit_system: Any | None
+) -> float | None:
+    visibility_miles = current.visibility_miles
+    visibility_km = current.visibility_km
+    if visibility_miles is None and visibility_km is not None:
+        visibility_miles = visibility_km * 0.621371
+    elif visibility_km is None and visibility_miles is not None:
+        visibility_km = visibility_miles * 1.60934
+
+    normalized_system = getattr(unit_system, "value", unit_system)
+    if normalized_system in {"us", "uk"}:
+        return visibility_miles
+    if normalized_system in {"ca", "si"}:
+        return visibility_km
+    if unit_pref == TemperatureUnit.CELSIUS:
+        return visibility_km
+    return visibility_miles
+
+
+def _resolve_visibility_unit_label(unit_pref: TemperatureUnit, unit_system: Any | None) -> str:
+    normalized_system = getattr(unit_system, "value", unit_system)
+    if normalized_system in {"us", "uk"}:
+        return "mi"
+    if normalized_system in {"ca", "si"}:
+        return "km"
+    if unit_pref == TemperatureUnit.CELSIUS:
+        return "km"
+    if unit_pref == TemperatureUnit.BOTH:
+        return "mi (km)"
+    return "mi"
+
+
+def _resolve_pressure_for_prompt(
+    current: Any, unit_pref: TemperatureUnit, unit_system: Any | None
+) -> float | None:
+    pressure_in = current.pressure_in
+    pressure_mb = current.pressure_mb
+    if pressure_in is None and pressure_mb is not None:
+        pressure_in = pressure_mb / 33.8639
+    elif pressure_mb is None and pressure_in is not None:
+        pressure_mb = pressure_in * 33.8639
+
+    normalized_system = getattr(unit_system, "value", unit_system)
+    if normalized_system == "ca":
+        return pressure_mb / 10 if pressure_mb is not None else None
+    if normalized_system in {"uk", "si"}:
+        return pressure_mb
+    if unit_pref == TemperatureUnit.CELSIUS:
+        return pressure_mb
+    return pressure_in
+
+
+def _resolve_pressure_unit_label(unit_pref: TemperatureUnit, unit_system: Any | None) -> str:
+    normalized_system = getattr(unit_system, "value", unit_system)
+    if normalized_system == "ca":
+        return "kPa"
+    if normalized_system in {"uk", "si"}:
+        return "hPa"
+    if unit_pref == TemperatureUnit.CELSIUS:
+        return "hPa"
+    if unit_pref == TemperatureUnit.BOTH:
+        return "inHg (hPa)"
+    return "inHg"
+
+
 def add_location_time_context(weather_dict: dict[str, Any], location: Any) -> None:
     """Add UTC and local time context for the selected weather location."""
     now_utc = datetime.now(UTC)

tests/test_ai_explainer.py

@@ -290,6 +290,34 @@ def test_to_prompt_text_with_time_info(self):
         assert "America/New_York" in prompt_text
         assert "afternoon" in prompt_text
 
+    def test_to_prompt_text_prefers_preformatted_unit_strings(self):
+        """Prompt text should use the already-resolved display units when provided."""
+        context = WeatherContext(
+            location="Toronto",
+            timestamp=datetime.now(UTC),
+            temperature=22.2,
+            temperature_unit="C",
+            conditions="Clear",
+            humidity=50,
+            wind_speed=16.1,
+            wind_direction="NW",
+            visibility=16.1,
+            pressure=101.8,
+            alerts=[],
+            temperature_text="22.2°C",
+            wind_text="16.1 km/h",
+            visibility_text="16.1 km",
+            pressure_text="101.76 kPa",
+        )
+        prompt_text = context.to_prompt_text()
+        assert "Temperature: 22.2°C" in prompt_text
+        assert "Wind: 16.1 km/h from NW" in prompt_text
+        assert "Visibility: 16.1 km" in prompt_text
+        assert "Pressure: 101.76 kPa" in prompt_text
+        assert "mph" not in prompt_text
+        assert "miles" not in prompt_text
+        assert "inHg" not in prompt_text
+
 
 # =============================================================================
 # ExplanationStyle Tests