var proxy_request = (System.Net.HttpWebRequest)System.Net.WebRequest.Create(
    "https://www.accuweather.com/en/us/st-paul-mn/55102/may-weather/348795?monyr=5/1/2018&view=table"
);
proxy_request.Credentials = System.Net.CredentialCache.DefaultCredentials;
proxy_request.Method = "GET";
proxy_request.ProtocolVersion = System.Net.HttpVersion.Version11;
proxy_request.Timeout = 5000;    // <-- щоб не було зависання.
proxy_request.KeepAlive = true;
proxy_request.Headers.Add("Upgrade-Insecure-Requests", "1");
proxy_request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36"
    + " (KHTML, like Gecko) Chrome/65.0.3325.181 Safari/537.36 OPR/52.0.2871.42";
proxy_request.Accept = "application/xhtml+xml;q=1,text/html;q=0.9,application/xml;q=0.8,*/*;q=0.7";
proxy_request.Headers.Add("Accept-Encoding", "gzip, deflate, br");
proxy_request.Headers.Add("Accept-Language", "uk,en;q=0.8,en-US;q=0.7");
// Щоб можна було переглянути вміст :
proxy_request.AutomaticDecompression = System.Net.DecompressionMethods.GZip;
// Щоб не було проблем з сертифікатом :
System.Net.ServicePointManager.ServerCertificateValidationCallback = (
    object sender,
    System.Security.Cryptography.X509Certificates.X509Certificate certificate,
    System.Security.Cryptography.X509Certificates.X509Chain chain,
    System.Net.Security.SslPolicyErrors sslPolicyErrors
    ) => true;
//
string html = "";
try {
    using(var resp = proxy_request.GetResponse() as System.Net.HttpWebResponse) {
        using(var sr = new System.IO.StreamReader(
                resp.GetResponseStream(), System.Text.Encoding.GetEncoding(1251)
            )) {
            html = sr.ReadToEnd();
            sr.Close();
        }
        resp.Close();
    }
}
catch(System.Net.WebException webEx) {
    MessageBox.Show(webEx.Message, "WebException");
}