If you have saved your latest temperature on your thermometer (you can read about how to do this here), the saved temperature is shown for a couple of seconds when you turn the thermometer back on.
Your thermometer will then show 37.00 °C (±0.01 °C, 36.99-37.01 °C) or 98.60 °F (±0.02 °F, 98.58-98.62 °F) when reloading.
You can view your saved temperature as many times as you wish, as long as you turn the thermometer off before the reloading value appears.
Please make sure that you don't miss the saved temperature and accidentally enter the thermometer’s reloading value into the app, as it is not your temperature.