I'm using the darksky api to get weather data for a display board website.
The free version is limited to 1000 api calls per month.
I have a lot of devices (iPads) diplaying this information in the building and refreshing every minute or so to update weather and the message of the hour
I think that caching the weather into a file and reading it when the refresh time is over is a solution to my problem.
Is it the best solution?
And is this the best implementation of this solution

function getWeather(){
//compares the time of the saved weather at each call of the method
$last_modif = filemtime("weather.json");

//if the weather is 10 minutes old, renew it by calling the api
if(time() - $last_modif > WEATHER_REFRESH_TIME){
    //echo "call api";
    $file = fopen("weather.json", "w");
    $request = 'https://api.darksky.net/forecast/MY_KEY/LAT,LNG?lang=fr&units=si&exclude=minutely,flags';
    $data = file_get_contents($request);
    fwrite($file,$data);
    fclose($file);
}

$file = fopen("weather.json", "r");
$weather = fread($file,filesize("weather.json"));
fclose($file);

return json_decode($weather);

}

Should i write the data in a database instead or is there any other way to store the weather?
What are the best practices in this case ?

I'm using the darksky api to get weather data for a display board website.

The free version is limited to 1000 api calls per month.
I have a lot of devices (iPads) displaying this information in the building and refreshing every minute or so to update weather and the message of the hour.

I think that caching the weather into a file and reading it when the refresh time is over is a solution to my problem.
Is it the best solution?
And is this the best implementation of this solution

function getWeather(){
    //compares the time of the saved weather at each call of the method
    $last_modif = filemtime("weather.json");

    //if the weather is 10 minutes old, renew it by calling the api
    if(time() - $last_modif > WEATHER_REFRESH_TIME){
        //echo "call api";
        $file = fopen("weather.json", "w");
        $request = 'https://api.darksky.net/forecast/MY_KEY/LAT,LNG?lang=fr&units=si&exclude=minutely,flags';
        $data = file_get_contents($request);
        fwrite($file,$data);
        fclose($file);
    }

    $file = fopen("weather.json", "r");
    $weather = fread($file,filesize("weather.json"));
    fclose($file);

    return json_decode($weather);
}

Should i write the data in a database instead or is there any other way to store the weather?
What are the best practices in this case ?