To measure the temperature you can use the simple towel, please note that you have a hot glow – please take care of your hand and note that you do not hold flammable substances over it. At a distance of about 12 cm above the glow the following rule of thumb applies:

Heat Temperature range After this time you pull your hand away
severe 230 to 290 centigrade 2 to 4 seconds
medium 170 to 230 centigrade 5 to 7 seconds
low 120 to 170 centigrade 8 to 10 seconds