char msg_buffer[60];
float temperature = 10.5;

void setup()
{
 Serial.begin(9600);
 char temp_str[15] = {0};
 dtostrf(temperature, 4, 1, temp_str);
 char *space = strchr(temp_str, ' ');
 if (space != NULL) {
  *space = '\0';
 }
 sprintf(msg_buffer, "Temperature: %s", temp_str);
 Serial.println(msg_buffer);
 pinMode(13, OUTPUT);
}

void loop() {}


/* alternative setup() */
void setup() {
 Serial.begin(9600);
 //create String object from float with 1 decimal place
 //will be heap-allocated
 String output = "Temperature " + String(temperature, 1);
 Serial.println(output);
 pinMode(13, OUTPUT);
}