Download_maps_program.cs

using System;
using System.Collections.Generic;
using System.Net;

namespace ConsoleApp20
{
    class Program
    {
        static void Main(string[] args)
        {
            var start = new DateTime(2018, 9, 1);
            var end = DateTime.Today;

            var dates = GetDateRange(start, end);
            var urls = GetUrls(dates);
            foreach (var url in urls)
            {
                using (WebClient wc = new WebClient())
                {
                    var filePath = "temprature_" + url.Item2.ToString("dd-MM-yyyy") + ".png";
                    wc.DownloadFile(url.Item1, filePath );
                }
            }
        }

        private static IEnumerable<Tuple<string, DateTime>> GetUrls(IEnumerable<DateTime> dates)
        {
            List<Tuple<string, DateTime>> urls = new List<Tuple<string, DateTime>>();
            foreach (var date in dates)
            {
                var url = $"http://model.ocean.univ.gda.pl/images/" + date.ToString("dd-MM-yyyy") + "_00/S_0_T_small.png";
                urls.Add(Tuple.Create(url, date));
            }

            return urls;
        }

        private static IEnumerable<DateTime> GetDateRange(DateTime start, DateTime end)
        {
            var dates = new List<DateTime>();

            for (var dt = start; dt <= end; dt = dt.AddDays(1))
            {
                dates.Add(dt);
            }

            return dates;
        }
    }
}