Let's say I took a thermometer and affixed it to the end of a poll. Then I went halfway across a bridge and held the other end of the poll and dipped the thermometer into the middle of a river and just held it there. Then I sent my friend upstream a bit and he walked halfway across a bridge up there and dropped one of those floating thermometers into the river and let it float / drift down the middle of the river toward me.
When the floating thermometer came drifting by me where I had the fixed thermometer I could see both thermometers at the same time. Would they both measure the same water temperature?
(Please allow me to say that the resin that affixed the thermometer to the poll was a perfect insulator. I.e. the thermometer was measuring the water temperature and none of the poll temperature.)