/**
 * Unit / localization configuration for weather output.
 *
 * The server defaults to imperial units (preserving historical behavior for
 * existing users). A server-wide default can be set via environment variables,
 * and individual tool calls may override it per request (see
 * `src/utils/unitPreferences.ts`).
 *
 * Environment variables:
 *   WEATHER_UNITS              imperial | metric            (default: imperial)
 *   WEATHER_TEMPERATURE_UNIT   F | C                        (override)
 *   WEATHER_WIND_SPEED_UNIT    mph | kmh | ms | kn          (override)
 *   WEATHER_PRECIPITATION_UNIT inch | mm                    (override)
 *   WEATHER_PRESSURE_UNIT      inHg | hPa                   (override)
 *   WEATHER_DISTANCE_UNIT      mi | km                      (override)
 *   WEATHER_TIME_FORMAT        12h | 24h                    (override)
 */
export type UnitSystem = 'imperial' | 'metric';
export type TemperatureUnit = 'F' | 'C';
export type WindSpeedUnit = 'mph' | 'kmh' | 'ms' | 'kn';
export type PrecipitationUnit = 'inch' | 'mm';
export type PressureUnit = 'inHg' | 'hPa';
export type DistanceUnit = 'mi' | 'km';
export type TimeFormat = '12h' | '24h';
/**
 * A fully-resolved set of unit preferences. Every weather output path formats
 * values according to one of these.
 */
export interface UnitPreferences {
    temperature: TemperatureUnit;
    windSpeed: WindSpeedUnit;
    precipitation: PrecipitationUnit;
    pressure: PressureUnit;
    distance: DistanceUnit;
    timeFormat: TimeFormat;
}
/** Imperial preset — the historical default. */
export declare const IMPERIAL_PREFERENCES: UnitPreferences;
/** Metric preset. */
export declare const METRIC_PREFERENCES: UnitPreferences;
/**
 * Return the base preset for a unit system.
 */
export declare function systemPreferences(system: UnitSystem): UnitPreferences;
/**
 * Accepted spellings for each unit, normalized to the canonical token.
 * Kept permissive so both the env layer and per-call params can share it.
 */
declare const NORMALIZERS: {
    readonly system: Map<string, UnitSystem>;
    readonly temperature: Map<string, TemperatureUnit>;
    readonly windSpeed: Map<string, WindSpeedUnit>;
    readonly precipitation: Map<string, PrecipitationUnit>;
    readonly pressure: Map<string, PressureUnit>;
    readonly distance: Map<string, DistanceUnit>;
    readonly timeFormat: Map<string, TimeFormat>;
};
/**
 * Normalize a raw string to a canonical unit token, or return undefined if the
 * value is unrecognized. Exported for reuse by the per-call resolver.
 */
export declare function normalizeUnit<K extends keyof typeof NORMALIZERS>(kind: K, raw: string | undefined): (typeof NORMALIZERS)[K] extends Map<string, infer V> ? V | undefined : never;
/**
 * The server-wide default unit preferences, resolved once at startup from the
 * environment. Per-call tool parameters layer on top of this.
 */
export declare const defaultUnitPreferences: UnitPreferences;
export {};
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