NullPointerException returns when I click daily button

 public class Forecast {

 private Current mCurrent;
    private Hour[] mHours;
    private Day[] mDays;

     public static int getIconID(String weather){
        switch (weather){
            case "clear-day":
                return R.drawable.clear_day;
            case "clear-night":
                return R.drawable.clear_night;
            case "rain":
                return R.drawable.rain;
            case "snow":
                return R.drawable.snow;
            case "sleet":
                return R.drawable.sleet;
            case "wind":
                return R.drawable.wind;
            case "fog":
                return R.drawable.fog;
            case "cloudy":
                return R.drawable.cloudy;
            case "partly-cloudy-day":
                return R.drawable.partly_cloudy;
            case "partly-cloudy-nigh":
                return R.drawable.cloudy_night;
            default:
                return R.drawable.sunny;
        }
    }

}````

private long mTime;
private String mSummary;
private double mTemperatureMax;
private String mIcon;
private String mTimeZone;

public int getIconID(){
    return Forecast.getIconID(mIcon); }

public class Adapter extends BaseAdapter {
    private Context mContext;
    private Day[] mDays;



    public Adapter(Context context, Day[] Day){
        mContext = context;
        mDays = Day;
    }


    @Override
    public int getCount() {
        return mDays.length;
    }

    @Override
    public Object getItem(int position) {
        return mDays[position];
    }

    @Override
    public long getItemId(int position) {
        return 0; ///used to tag items for easy items
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder;

        if (convertView == null){
            convertView = LayoutInflater.from(mContext).inflate(R.layout.daily_list_item, null);
            holder = new ViewHolder();
            holder.dayLabel = (TextView) convertView.findViewById(R.id.DayName_Daily);
            holder.iconImageView = (ImageView) convertView.findViewById(R.id.IconWeather_Daily);
            holder.temperatureLabel = (TextView) convertView.findViewById(R.id.TemperatureLabel_Daily);

            convertView.setTag(holder);
        }
        else {
            holder = (ViewHolder) convertView.getTag();
        }

        Day day = mDays[position];
        holder.iconImageView.setImageResource(day.getIconID());
        holder.temperatureLabel.setText(day.getTemperatureMax()+"");
        holder.dayLabel.setText(day.getDayOfTheWeek());
        return convertView;
    }


    private static class ViewHolder{
        ImageView iconImageView;
        TextView temperatureLabel;
        TextView dayLabel;
    }
}