gas.js

// 取得するJSONのURL
var url = "http://api.openweathermap.org/data/2.5/weather?lat=35.65858&lon=139.745433";

// データを保存するシート
var data_sheet_name = 'data';

// アップデートするチャートの名前
var chart_sheet_name = 'charts';
var chart_name = 'Temps';

// JSONのデータを配列に変換
var data_to_line = function(data) {
  return [new Date(), data.main.temp, data.main.humidity];
}

function fetchJSON() {
  var response = UrlFetchApp.fetch(url);
  if (response.getResponseCode() == 200) {
    var data = Utilities.jsonParse(response.getContentText());
    
    var doc = SpreadsheetApp.getActiveSpreadsheet();
    var data_sheet = doc.getSheetByName(data_sheet_name);
    appendDataToBottom(data_sheet, data);
    
    var charts_sheet = doc.getSheetByName(chart_sheet_name);
    updateChart(charts_sheet, chart_name, data_sheet, 4);
  }
}

function appendDataToBottom(sheet, data) {
  var start_row = sheet.getLastRow() + 1;
  var line = data_to_line(data);
  sheet.getRange(start_row, 1, 1,line.length).setValues([line]);
}

function updateChart(charts_sheet, chart_title, data_sheet, cols) {  
  var charts = charts_sheet.getCharts();
  for (var i in charts) {
    var chart = charts[i];
    if(chart.getOptions().get("title") == chart_title) {
      var builder = chart.modify();
      var ranges = chart.getRanges();
      for (var j in ranges) {
        builder.removeRange(ranges[j]);
      }
      var newRange = data_sheet.getRange(1, 1, data_sheet.getLastRow()+1, cols);
      builder.addRange(newRange);
      charts_sheet.updateChart(builder.build());
    }
  }
}