How to access weather API rain data with async function

I am working with OpenWeatherMap API to calculate the sum of precipitation for the previous 5 days. I have no issues accessing values such as humidity or temp, but I am having issues totaling all rain values of the previous 5 days. rain is only available in the object response with it is actually measured. here is an example of what it look like when rain is measured: enter image description here

You can see that rain is under hourly.18.rain[‘1h’]. My issue comes in totaling them all.

Here is my full code:

//converts current unix date from miliseconds to seconds and subtracts seconds from variable daysAgo
function getDaysAgo(days) {
    return Math.floor(( / 1000) - (86400 * days)) //returns date of privious 5 days from now.
//fetchs historic hourly weather data for rain.
async function getDataForDaysAgo(days) {
    let daysAgo = getDaysAgo(days) //nest getDaysAgo function to variable
    const apiURL = `${daysAgo}&appid=` //calls historic weather api using privious days
    const apiResponse = await fetch(apiURL)  //fetch data
    const responseJson = await apiResponse.json() //converts data to json
    var total = 0

    responseJson.hourly.forEach(hour => { //loops through each 1hr record of 24
          //if no rain is recorded, rain data is not available. system reprots: NaN
          if (isNaN(hour.rain['1h'])){
            hour.rain['1h'] = 0   //if rain is NaN, change that value to 0.
          }//else(total += hour.rain);
            total += hour.rain['1h']
          }//otherwise sum all available rain values.
          //total += hour.rain

    console.log(`getDataForDaysAgo(${days}) returns ${total}`) //logs total rain values for each 24hr period
    return total
//call above fetch function with appropriate historic 'daysAgo'
async function getDataSums() {
    var data1 = await getDataForDaysAgo(5)
    var data2 = await getDataForDaysAgo(4)
    var data3 = await getDataForDaysAgo(3)
    var data4 = await getDataForDaysAgo(2)
    var data5 = await getDataForDaysAgo(1)
    return data1 + data2 + data3 + data4 + data5; //returns sum of 5 day rain values

getDataSums().then(result => { //waits for getDataSums and return result
    var totalRainInches = parseFloat((result)*25.4); //converts to mm to inches
      document.getElementById('precip5day').innerHTML = "Five Day Precipication Accumulation:"
      document.getElementById('precipValue').innerHTML = totalRainInches.toFixed(2) + "″"
    //proof of concept conditional statment that gives recommendations for trail use
    //based on 5 day rain totals and writes to index.html file
    if (totalRainInches <= 0.50){
      document.getElementById('conditions').innerHTML = "Hiking and mountain biking should be okay"
    } else if (totalRainInches < 3 ){
      document.getElementById('conditions').innerHTML = "Due to recent rain activity, use best judgement when hiking or mountain biking"
    } else if (totalRainInches > 7 ){
      document.getElementById('conditions').innerHTML = "Due to heavy rainfall, trails should not be used"
    }else {
      document.getElementById('conditions').innerHTML = "Something broke :("

I had luck totaling all of the humidity values with:

    responseJson.hourly.forEach(hour => {
          if (isNaN(hour.humidity)){
            hour.humidity = 0   
            total += hour.humidity

but when it comes to the rain values I am coming up empty handed and receiving error messages that the rain variable is undefined. Any thought? Thanks! Also, here is a link to a previous question that got me this far.


Are you sure that rain is present in all hours from 0 to 23? If it’s missing you’d get "Uncaught TypeError: Cannot read property '1h' of undefined" like in my sample below. If you check for it, it should sum it up alright.

// prep 24 hours with rain and humidity
var hourly = []
for (let i = 0; i < 24; i++) {
  hourly[i] = {
    rain: {
      '1h': 0.5
    humidity: 2.2

// your code in a function
function sumRain(hourly) {
  var total = 0;
  hourly.forEach(hour => {
    // uncomment the next line to check for 'rain' being present
    // if (hour.rain)
    if (isNaN(hour.rain['1h'])) {
      hour.rain['1h'] = 0
    } else {
      total += hour.rain['1h']

  return total;


// modify hourly so rain is missing from one of the hours
delete hourly[11].rain;

// now sumrain throws an exception unless you check for hour.rain being present before trying to sum it up