NSUnknownKeyExeption for the key humidity?

import UIKit

class ViewController: UIViewController {

    // links to labels

    @IBOutlet weak var iconView: UIImageView!
    @IBOutlet weak var currentTimeLabel: UILabel!
    @IBOutlet weak var temperatureLabel: UILabel!
    @IBOutlet weak var humidityLabel: UILabel!
    @IBOutlet weak var precipitationLabel: UILabel!
    @IBOutlet weak var summaryLabel: UILabel!


    private let apiKey = "3a365c222ac8e460cdff4d4514dfe407"

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view, typically from a nib.

        //let forecastURL = "https://api.forecast.io/forecast/3a365c222ac8e460cdff4d4514dfe407/39.630016,-76.331865"

        let baseURL = NSURL(string: "https://api.forecast.io/forecast/\(apiKey)/")
        let forecastURL = NSURL(string: "39.630016,-76.331865", relativeToURL: baseURL)

        //the following code makes our request syncronous and would tie up the app - not good
        // we want asyncronous code so we can use multiple threads of execution simultaneously

        //let weatherData = NSData(contentsOfURL: forecastURL!, options: nil, error: nil)
         //println(weatherData)      


        let sharedSession = NSURLSession.sharedSession()
        let downloadTask: NSURLSessionDownloadTask = sharedSession.downloadTaskWithURL(forecastURL!, completionHandler: {(location: NSURL!, response: NSURLResponse!, error: NSError!) -> Void in
           // println(response)

            // test to see if we are getting data from the URL
           // var urlContents = NSString(contentsOfURL: forecastURL!, encoding: NSUTF8StringEncoding, error: nil)
            //println(urlContents)

            // want to hold contents in a file

            if (error == nil) {

            let dataObject = NSData(contentsOfURL: location)
            let weatherDictionary: NSDictionary = NSJSONSerialization.JSONObjectWithData(dataObject!, options: nil, error: nil) as NSDictionary

            let currentWeather = Current(weatherDictionary: weatherDictionary)

                dispatch_async(dispatch_get_main_queue(), { () -> Void in
                    self.temperatureLabel.text = "\(currentWeather.temperature)"
                    self.iconView.image = currentWeather.icon!
                    self.currentTimeLabel.text = "At \(currentWeather.currentTime!) it is"
                    self.humidityLabel.text = "\(currentWeather.humidity)"
                    self.precipitationLabel.text = "\(currentWeather.precipProbability)"
                    self.summaryLabel.text = "\(currentWeather.summary)"              
                })

            }

        })

        downloadTask.resume()        

    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }    

}

import Foundation
import UIKit

struct Current {

    var currentTime: String?
    var temperature: Int
    var humidity: Double
    var precipProbability: Double
    var summary: String
    var icon: UIImage?
    init (weatherDictionary: NSDictionary) {

        let currentWeather = weatherDictionary["currently"] as NSDictionary

        temperature = currentWeather["temperature"] as Int
        println(temperature)
        humidity = currentWeather["humidity"] as Double
        precipProbability = currentWeather["precipProbability"] as Double
        summary = currentWeather["summary"] as String


        let currentTimeIntValue = currentWeather["time"] as Int
        currentTime = dateStringFromUnixtime(currentTimeIntValue)

        let iconString = currentWeather["icon"] as String
        icon = weatherIconFromString(iconString)

    }


    func dateStringFromUnixtime(unixTime: Int) -> String {
         let timeInSeconds = NSTimeInterval(unixTime)
        let weatherDate = NSDate(timeIntervalSince1970: timeInSeconds)

        let dateFormatter = NSDateFormatter()
        dateFormatter.timeStyle = .ShortStyle
        return dateFormatter.stringFromDate(weatherDate)



    }


    func weatherIconFromString(stringIcon: String) -> UIImage {
        var imageName: String

        switch stringIcon {

        case "clear-day":
            imageName = "clear-day"
        case "clear-night":
            imageName = "clear-night"
        case "rain":
            imageName = "rain"
        case "snow":
            imageName = "snow"
        case "sleet":
            imageName = "sleet"
        case "wind":
            imageName = "wind"
        case "fog":
            imageName = "fog"
        case "cloudy":
            imageName = "cloudy"
        case "partly-cloudy-day":
            imageName = "partly-cloudy"
        case "partly-cloudy-night":
            imageName = "cloudy-night"
        default:
            imageName = "default"
        }
        var iconImage = UIImage(named: imageName)
        return iconImage!

    }


}