Can't perform what seems like a simple HTTP POST to openweathermap.org

问题

My function in an Angular service component to POST a request to create a new weather station with openweathermap.org:

registerStation(registerWeatherStation: RegisterWeatherStation): Observable<Response> {
let params = JSON.stringify(registerWeatherStation)
console.log("params: ",params)
let header = new Headers({'Content-Type': 'application/json; charset=utf-8'})
let options = new RequestOptions({ headers: header })
let url = this.servUrl + 'stations?appid=' + this.weatherAppId
return this
    .http
    .post(url, params, options)
}

This is from Chrome's Developer Tools Network Tab showing activity triggered by the above function. I think this shows my preflight request, preflight response from openweathermap.org, and my request headers:

Preflight Request???  
request url: http://api.openweathermap.org/data/3.0/stations?appid=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx  
Request Method: OPTIONS  
Status Code: 404 Not Found  
Remote Address: 162.243.53.59:80  
Referrer Policy: no-referrer-when-downgrade  

Response Headers  
Access-Control-Allow-Credentials: true  
Access-Control-Allow-Methods: GET, POST, PUT, DELETE  
Access-Control-Allow-Origin: *  
Connection: keep-alive  
Content-Length: 42  
Content-Type: application/json; charset=utf-8  
Date: Thu, 24 May 2018 19:57:00 GMT  
Server: openresty  

Request Headers  
Accept: */*  
Accept-Encoding: gzip, deflate  
Accept-Language: en-US,en;q=0.9  
Access-Control-Request-Headers: content-type  
Access-Control-Request-Method: POST  
Connection: keep-alive  
Host: api.openweathermap.org  
Origin: http://localhost:54270  
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3359.181 Safari/537.36

This is Postman's code snippet of the POST I performed that got a valid response from openweathermap.org:

POST /data/3.0/stations?appid=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx HTTP/1.1
Host: api.openweathermap.org
Content-Type: application/json
Cache-Control: no-cache
Postman-Token: 25e03224-a9e7-43af-9757-dc37c41af780

{"external_id":"Paula's_Ranch_1","name":"Paula's Ranch Weather","latitude":xx.155012,"longitude":-xxx.976649,"altitude":100}

What am I doing wrong? Should I perform the post from my backend?