How to find the Average with No LINQ code !

Question

<pre> public static TheWeather GetAverageForMonth(List<TheWeather> entries, int year, int month)

{

TheWeather GetItem = entries.First();

return GetItem;

}</pre>

from this method i would like to find the Avergage for EX year 2018, month = 5 which they are already saved in the List <TheWeather> and the The Class TheWeather has the Properties :

<pre>public class TheWeather

{

public DateTime dateTime { get; set; }

public double Actual_mean_temp { get; set; }

public double Record_min_temp { get; set; }

public double Record_max_temp { get; set; }

public double Actual_precipitation { get; set; }

}</pre>

without using the LINQ i would like to find the Average please .