首先将您的TodayHourse.fromJson更改为：

TodayHourse.fromJson(Map<String, dynamic> json)
      : datetime = json['datetime'],
        dateEpoch = json['datetimeEpoch'],
        conditions = json['conditions'],
        temp = json['temp'],
        windDir = json['winddir'],
        windSpeed = json['windspeed'],
        humidity = json['humidity'],
        visibility = json['visibility'];

你的hours是Map的列表，你不需要使用json['days'][0]。然后在你的TodayWeather.fromJson中，将hours更改为：

hours = (json['days'][0]['hours'] as List).map((x) => TodayHourse.fromJson(x)).toList();

你使用了错误的函数代替toJson，你需要调用TodayHourse.fromJson(x)。

尝试使用此模型：

class TodayWeather {
  TodayWeather({required this.days});

  final List<Day> days;

  factory TodayWeather.fromJson(Map<String, dynamic> json) => TodayWeather(
        days: List<Day>.from(json["days"].map((x) => Day.fromJson(x))),
      );
}

class Day {
  Day({
    required this.datetime,
    required this.datetimeEpoch,
    required this.tempmax,
    required this.tempmin,
    required this.temp,
    required this.windspeed,
    required this.winddir,
    required this.visibility,
    required this.sunrise,
    required this.sunset,
    required this.conditions,
    required this.hours,
  });

  final DateTime datetime;
  final int datetimeEpoch;
  final double tempmax, tempmin, temp, windspeed, winddir, visibility;
  final String sunrise, sunset, conditions;
  final List<Hour> hours;

  factory Day.fromJson(Map<String, dynamic> json) => Day(
        datetime: DateTime.parse(json["datetime"]),
        datetimeEpoch: json["datetimeEpoch"],
        tempmax: json["tempmax"].toDouble(),
        tempmin: json["tempmin"].toDouble(),
        temp: json["temp"].toDouble(),
        windspeed: json["windspeed"].toDouble(),
        winddir: json["winddir"].toDouble(),
        visibility: json["visibility"].toDouble(),
        sunrise: json["sunrise"],
        sunset: json["sunset"],
        conditions: json["conditions"],
        hours: List<Hour>.from(json["hours"].map((x) => Hour.fromJson(x))),
      );
}

class Hour {
  Hour({
    required this.datetime,
    required this.datetimeEpoch,
    required this.temp,
    required this.humidity,
    required this.windspeed,
    required this.winddir,
    required this.visibility,
    required this.conditions,
  });

  final int datetimeEpoch;
  final double temp, humidity, windspeed, winddir, visibility;
  final String datetime, conditions;

  factory Hour.fromJson(Map<String, dynamic> json) => Hour(
        datetime: json["datetime"],
        datetimeEpoch: json["datetimeEpoch"],
        temp: json["temp"].toDouble(),
        humidity: json["humidity"].toDouble(),
        windspeed: json["windspeed"].toDouble(),
        winddir: json["winddir"].toDouble(),
        visibility: json["visibility"].toDouble(),
        conditions: json["conditions"],
      );
}

首先，为了更清楚地解析JSON数组，您可以在模型中创建helper方法，我将其命名为Model.fromJsonList

static List<WeatherDay> fromJsonList(dynamic jsonList) {
    if (jsonList == null || jsonList.isEmpty) return [];
    return (jsonList as List).map((e) => WeatherDay.fromJson(e)).toList();
  }

因此，通过这种方法，你可以解析数组响应非常容易和干净，例如：

Future<WeatherDay> fetchTodayWeather() async {
    final response = await httpClient.get(
        '36.31559%2C59.56796/today?unitGroup=metric&key=Key&contentType=json');
    final List<WeatherDay> weatherDays = WeatherDay.fromJsonList(response.data["days"]);
    return weatherDays.first;
  }

我们总共有：

class WeatherDay {
  WeatherDay( {
    @required this.datetime,
    @required this.hours,
  });

  final String datetime;
  final List<WeatherHour> hours;

  factory WeatherDay.fromJson(Map<String, dynamic> json) {
    return WeatherDay(
      datetime: json['datetime'] as String,
      hours: WeatherHour.fromJsonList(json['hours']),
    );
  }

  static List<WeatherDay> fromJsonList(dynamic jsonList) {
    if (jsonList == null || jsonList.isEmpty) return [];
    return (jsonList as List).map((e) => WeatherDay.fromJson(e)).toList();
  }
}

class WeatherHour {
  WeatherHour( {
    @required this.dateEpoch,
    @required this.conditions,
  });

  final num dateEpoch;
  final String conditions;

  factory WeatherHour.fromJson(Map<String, dynamic> json) {
    return WeatherHour(
      dateEpoch: json['datetimeEpoch'] as num,
      conditions: json['conditions'] as String,
    );
  }

  static List<WeatherHour> fromJsonList(dynamic jsonList) {
    if (jsonList == null || jsonList.isEmpty) return [];
    return (jsonList as List).map((e) => WeatherHour.fromJson(e)).toList();
  }
}

• • Note**：我没有分析所有的变量，你自己做吧。