I created a real-time graph on Processing that tracks weather data like Humidity, Temperature, and Pressure. Yet, it seems that my graph begins with a steep spike and then corrects itself. How do I remove the initial spike in my graph? Does anyone have good ideas on how to do this? Thanks.

Below I posted my code for reference.

Here is my code:

  import processing.serial.*;
  Serial myPort;
  String inBuffer = "";
  float Humidity = 0;
  float Temperature = 0;
  float Pressure = 0;
  int dataCount = 1;
  int loopCount = 0;

  boolean first_comm = true;

  float[] dat = new float[625];
  float[] Humidity_array = new float[625];
  int[] Temperature_array = new int[625];
  int[] Pressure_array = new int[625];

  PFont font;

   void setup() {
    size(1024, 768);
    String portName = Serial.list()[0];
    myPort = new Serial(this, portName, 115200);
    delay(500);
    myPort.bufferUntil ('\n');
    smooth();
    font = loadFont("Times-Roman-22.vlw");
    textFont(font);
    frameRate(10);
  }

  void serialEvent(Serial myPort) {
    int start = 0;
    if (first_comm == true)
    {
      start = 4;
      first_comm = false;
    }
    inBuffer = myPort.readStringUntil('\n');
    inBuffer = inBuffer.substring(0, inBuffer.length()- 1);
    dat = float(split(inBuffer, ',')); 
    dataCount ++;
    if (dataCount > 2) {
      Humidity = (dat[0]*100);
      Temperature = (dat[1]/10);
      Pressure = (dat[2]/1000);
    }
  }

  void draw() {
    background(255);
    fill(0);
    if (dataCount == 2) {
      for (int i = 0; i<dat.length;i++)
      {
        dat[i] = 0;
      }
    }
    //Axes Labels
    textSize(14);
    text("0,-30\u00B0, 88.1", 2, 755);
    text("9, -23.25\u00B0, 90.2", 2, 700);
    text("15, -18\u00B0, 91.6", 2, 660);
    text("28, -9\u00B0, 94.4", 2, 580);
    text("40, 0\u00B0, 97.2", 2, 500);
    text("52, 9\u00B0, 100", 2, 420);
    text("64, 18\u00B0, 102.8", 2, 340);
    text("76, 27\u00B0, 105.6", 2, 260);
    text("82, 31.5\u00B0, 107", 2, 220);
    text("100, 45\u00B0, 111.2", 2, 100);
    text("Humidity (%), Temperature (C), Pressure (kPa)", 2, 65);

    //Time (Seconds)
    textSize(16);
    text("Time (s)", 800, 755);
    text("Now", 610, 755);
    text("-10", 510, 755);
    text("-20", 410, 755);
    text("-30", 310, 755);
    text("-40", 210, 755);

    //Graph Name
    textSize(15);
    text("Outdoor Weather", 300, 30);

    //Graph Legend
    textSize(15);
    text("Graph Legend:", 825, 70);
    fill(109, 207, 71);
    text("Humidity", 840, 100);
    fill(109, 41, 71);
    text("Temperature", 830, 130);
    fill(37, 87, 223);
    text("Pressure", 840, 160);

    //Data
    fill(115, 115, 115);
    textSize(14);
    text("Humidity:" + " " + Humidity + "%", 800, 400);
    text("Temperature:" + " " + Temperature + "\u00B0C", 800, 430);
    text("Pressure:" + " " + Pressure + " kPa", 800, 460);

    //Grid Lines
    for (int i = 0 ;i<=width/18.75;i++)
    {
    strokeWeight(1);
    stroke(225);
    line((-frameCount%20)+i*20-450, 100, (-frameCount%20)+i*20-450, height);
    line(0, i*20+100, width-400, i*20+100);
    }
    //Humidity Line
    float var_scale_h = map(Humidity, 0, 100, 768, 100);
    noFill();
    stroke(109, 207, 71);
    strokeWeight(5);
    Humidity_array[Humidity_array.length-1]= int(var_scale_h);
    if (dataCount > 2) {
    beginShape();
    for (int i = 0; i<Humidity_array.length;i++)
    {
        vertex(i, Humidity_array[i]);
    }
    endShape();
    for (int i = 1; i<Humidity_array.length;i++)
    {
      Humidity_array[i-1] = Humidity_array[i];
    }

    //Temperature Line
    float var_scale_t = map(Temperature, -30, 45, 768, 100);
    noFill();
    stroke(109, 41, 71);
    strokeWeight(5);
    beginShape();
    Temperature_array[Temperature_array.length-1]= int(var_scale_t);
    for (int i = 0; i<Temperature_array.length;i++)
    {
      vertex(i, Temperature_array[i]);
    }
    endShape();
    for (int i = 1; i<Temperature_array.length;i++)
    {
      Temperature_array[i-1] = Temperature_array[i];
    }

    //Pressure Line
    float var_scale_p = map(Pressure, 89.5, 110, 768, 100);
    noFill();
    stroke(37, 87, 223);
    strokeWeight(5);
    beginShape();
    Pressure_array[Pressure_array.length-1]=int(var_scale_p);
    for (int i = 0; i<Pressure_array.length;i++)
    {
      vertex(i, Pressure_array[i]);
    }
    endShape();
    for (int i = 1; i<Pressure_array.length;i++)
    {
      Pressure_array[i-1] = Pressure_array[i];
    }
    loopCount ++;
  }
}