Operation timed out (but why?)

[phuz]

I am using a wunderground.com feed to grab weather to display in my app. The data source is valid, and I have the timer ticking every 300 seconds as to not overload the connection, but it's causing my app to run slow and sometimes become unresponsive, which throws an exception for operation timed out.
Here is my routine which is causing problems. If I try to hit that URL in my browser, it loads in about 2 seconds and I can keep hammering it repeatedly without becoming slow. Is there a better method to grab the data I want?

I appreciate any insight.

 
Imports System.Runtime.InteropServices
Imports System.Threading
Imports System.Net, System.Text.RegularExpressions

Public Class Form1
    Private Function GetBetween(ByVal Input As String, ByVal STR1 As String, ByVal STR2 As String, ByVal Index As Integer) As String
        Return Regex.Split(Regex.Split(Input, STR1)(Index + 1), STR2)(0)
    End Function

    Dim HookL As New UpdateLabel(AddressOf UL)
    Delegate Sub UpdateLabel(ByVal Label As TextBox, ByVal Text As String)

    Sub UL(ByVal Label As TextBox, ByVal Text As String)
        If Me.InvokeRequired Then
            Invoke(New UpdateLabel(AddressOf UL), Label, Text)
        Else
            Label.Text = Text
        End If
    End Sub

    Sub GetWeather() 'Handles weatherUpdateTimer.Tick
        Try
            Dim Source As String = New WebClient().DownloadString("http://m.wund.com/cgi-bin/findweather/getForecast?brand=mobile&query=19608")

            UL(TextBox1, GetBetween(Source, "<span class=""nowrap""><b>", "</b>", 0))
            UL(TextBox2, GetBetween(Source, "<td><b>", "%</b></td></tr>", 0))
            UL(TextBox3, GetBetween(Source, "<tr><td>Wind</td>", "</b>&nbsp;mph</span>", 0))
            UL(TextBox4, GetBetween(TextBox3.Text, "<span class=""nowrap""><b>", "</b>&nbsp;mph</span>", 0))
            UL(TextBox5, GetBetween(Source, "High of ", "F.", 0))
            UL(TextBox6, GetBetween(Source, "Low of ", "F.", 0))

            'Dim Radar As String = GetBetween(Source, "<br /><a href=""", """>Zoom into", 1)
        Catch ex As Exception
            System.Console.WriteLine("Weather Exception: " + ex.Message)
            MsgBox("Weather Exception: " + ex.Message)
        End Try

    End Sub
End Class

[kareninstructor]

High level consider WebClient.DownloadFileAsync in tangent with a BackGroundWorker or via Async/Await, a few simple starter examples.

[phuz]

Thank you!