How to return a promise that resolves customized data from API Javascript

So I’m using the API of National Weather Service to create a weather app. But the fetched data is very complicated, and I need to fetch two different APIs. So I want to write a customized async function that returns a promise, which resolves to an object that contains only the necessary data I need.

I came up with something like this:

async function fetchWeatherAPI(){
    //data that I need
    let data = {};
    
    try {
       const res1 = await fetch(url1);
       const result1 = await res1.json();
       data = {...data , result1.usefulData};
    } catch(error){}

    try {
       const res2 = await fetch(url2);
       const result2 = await res2.json();
       data = {...data, result2.usefulData};
    } catch(error){}

    return new Promise((resolve,reject)=>{
         resolve(data);
    })

}

This code is working for me. But the problem is, what if the APIs reject? How can I handle the error so that I can display the error message in the returned promise? I may want something like this:

return new Promise((resolve,reject)=>{
    if(...) reject(errrorMessage); 
    resolve(data);
})