I would compare it to some other thermometer. If nothing else you could take it inside and put it next to your house thermostat. Give it a couple of hours to settle down and then compare the reading to what the thermostat says.
I have a pool THERMOMETER and I don't think the reading is correct. It is one just like this View attachment 31202. I have it under the water about 6 inches and the reading on it always seems warmer than the water feels. are theses kinds of THERMOMETERS accurate? Thanks.
I would compare it to some other thermometer. If nothing else you could take it inside and put it next to your house thermostat. Give it a couple of hours to settle down and then compare the reading to what the thermostat says.