You have a bug in your tests. Fix it.

using System;
using System.IO;

namespace Treehouse.CodeChallenges
{
    public class Program
    {
        public static void Main(string[] arg)
        {
            var wf = WeatherForecast.ParseWeatherForecast(new string[] {"HGKL8Q","06/11/2016 0:00","Rain","53","0.3","0.03"} ) as WeatherForecast;
            Console.WriteLine(wf.WeatherStationId);
        }
    }
}

using System;

/* Sample CSV Data 

weather_station_id,time_of_day,condition,temperature,precipitation_chance,precipitation_amount
HGKL8Q,06/11/2016 0:00,Rain,53,0.3,0.03
HGKL8Q,06/11/2016 6:00,Cloudy,56,0.08,0.01
HGKL8Q,06/11/2016 12:00,PartlyCloudy,70,0,0
HGKL8Q,06/11/2016 18:00,Sunny,76,0,0
HGKL8Q,06/11/2016 19:00,Clear,74,0,0
*/

namespace Treehouse.CodeChallenges
{
    public class WeatherForecast
    {
        public string WeatherStationId { get; set; }

        public static WeatherForecast ParseWeatherForecast(string[] values)
        {
            var weatherForecast = new WeatherForecast();

            weatherForecast.WeatherStationId = values[0];

            return weatherForecast as WeatherForecast;
        }
    }
}