Should we choose a sunny place or a cool place to measure the temperature?

Generally speaking, the temperature is measured in the shade. By the way, let me explain why meteorologists prefer to measure temperature in the shade rather than in the sun. It turns out that only a thermometer placed in the shade can measure the temperature of the air. If you put the thermometer in the sun, the sun will make it much hotter than the surrounding air, so the degree indicated on the thermometer is no longer the temperature of the surrounding air. So it is meaningless to measure the temperature with a thermometer in the sun.