Spring multi thread to update same table but different row

Question

Currently, I am working on my personal Spring project on temperature data.

So basically there is an H2 database and a table containing different regions with the current temperature in that region.

And the temperature is fake data, just a random int generated within a random time range between 1-5 seconds. (Simulating the real world temperature are changing over time)

@Entity
@Transactional
@Table(name = "REGIONAL_WEATHER")
public class Weather {
    @Id
    @GeneratedValue
    private int ID;
    private String region;
    private Integer temperature;
    //getter setter constructor..
}

My question is I would like to try to update the table for each region in a faster way, so I designed to update it with multithreading, but I don't know am I doing it right, because some rows are not updated while the application is running... Serivce class:

@Service
public class WeatherService {
    private WeatherRepository weatherRepository;

    @Autowired
    public WeatherService(WeatherRepository weatherRepository) {
        this.weatherRepository = weatherRepository;
    }

    @Async
    public CompletableFuture updateTemperature(String region)throws Exception{
        double result = generateData(region);
        return CompletableFuture.completedFuture(result);
    }

    public double generateData(String region) throws InterruptedException {
        Random random = new Random();
        Integer randomInt = random.nextInt(5) + 1;
        Thread.sleep(randomInt * 1000);
        
        Integer randomTemp = random.nextInt(40) + 10;
        weatherRepository.updateTemp( region, randomTemp);
        Optional<Weather> ow = weatherRepository.findTempByRegion("AAPL");
        if (ow.isPresent()) {
            return ow.get().getTemperature;
        }
        return 0.0;
    }
}

And I use CommandRunner to run my thread:

@Component
public class AppRunner implements CommandLineRunner {

    private final WeatherService weatherService;

    @Autowired
    public AppRunner(WeatherService weatherService) {
        this.weatherService = weatherService;
    }

    @Override
    public void run(String... args) throws Exception {
        while(true){
            CompletableFuture<Weather> page1 = weatherService.updateTemperature("USA");
            CompletableFuture<Weather> page2 = weatherService.updateTemperature("UK");
            CompletableFuture<Weather> page3 = weatherService.updateTemperature("CA");
            CompletableFuture<Weather> page4 = weatherService.updateTemperature("JP");
            page1.get();
            page2.get();
            page3.get();
            page4.get();
        }
    }
}

It works but it is not working properly, because not all the rows are updating Only 2 out of 4 rows are updating. Can please someone tell me why and any good suggestions on it?