Java Picture Frame ???

[shqiptari]

Hello,
I am new to Java, but I need to implement a an mvc program to display some temperature gui. Also I want to Display 4 pic to show the seasons based on temperature range,
I am having trouble with this thing, because it just shows the first picture

import java.awt.*;
import java.awt.event.*;
import java.util.Observable;
import java.util.Observer;
@SuppressWarnings("serial")
public class DisplayPic extends Frame implements Observer {
	private TemperatureModel model;
	private Image img;
	private String imagePath = null;
	private int temperatureF;

	public DisplayPic(TemperatureModel model, int h, int v) {
		super("Image Frame");
		this.model = model;
		int temperatureF = (int) model().getF();
		if (temperatureF <= 40)
			imagePath = "winter.gif";
		else if (temperatureF > 40 && temperatureF <= 80)
			imagePath = "spring.gif";
		else if (temperatureF > 80 && temperatureF <= 140)
			imagePath = "fall.gif";
		else
			imagePath = "summer.gif";
		MediaTracker mt = new MediaTracker(null);
		img = Toolkit.getDefaultToolkit().getImage(imagePath);
		mt.addImage(img, 0);
		setSize(400, 400);
		setVisible(true);
		model.addObserver(this); // Connect to the model
		addWindowListener(new TemperatureGUI.CloseListener());
	}

	public void update(Graphics g) {
		paint(g);
	}

	public void paint(Graphics g) {
		temperatureF = (int) model().getF();
		if (img != null)
			g.drawImage(img, 100, 100, null);
		else
			g.clearRect(0, 0, getSize().width, getSize().height);
		super.paint(g);
	}

	protected TemperatureModel model() {
		return model;
	}

	@Override
	public void update(Observable obs, Object o) {
		repaint();		
	}

}

This is my code, this class is called then in the mvc convert class which serves as a main.

I want to change the picture with respect to the specified ranges,
but the problem is that for some reason when the user changes the pic in the scree this is not updated in the program, does it have to do with the implementation of any Listener, BTW model().getF() always changes when the temp changes ( it takes the temperature)