Sample code of grabbing temperature value and then either leaving as-is or converting to °C.

temperature.m

// Round temperature values to whole integers
NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init];
[numberFormatter setMaximumFractionDigits:0];
[numberFormatter setRoundingMode: NSNumberFormatterRoundUp];

// Get the current temp from Current Forecast JSON
// Default is °F, convert to °C if User Settings is set to Celcius (0)
if (unitTemp == 1) {
    currentTemp = [numberFormatter stringFromNumber:[currently valueForKeyPath:@"temperature"]];
}
else {
    CGFloat nCurrentTemp = [[currently valueForKeyPath:@"temperature"] floatValue];
    CGFloat valConvertedTemp = (nCurrentTemp - 32) * 0.5556;
    
    NSNumber *dispConvertedTemp = [NSNumber numberWithFloat:valConvertedTemp];
    currentTemp = [numberFormatter stringFromNumber:dispConvertedTemp];
}