Does water temperature impact TDS readings?

Conductivity of ions in water depends upon temperature. There are a number of factors that cause this effect, but a major one is simply that the ions naturally move around faster as they get warmer. When the same numbers of ions are moving faster, the apparent conductivity is increased. The relationship between conductivity and temperature is complicated and dependent on the solution being tested.

Pure water responds fairly linearly with temperature, with its conductivity rising by 4.55% for every degree centigrade (2.5% per degree Fahrenheit). Sodium chloride solutions have a smaller change, about 2.12% per degree centigrade. Tap and other natural waters have many different ions in them, and such systems sometimes respond nonlinearly with temperature changes, but not typically to as great of an extent as does pure water.

For this reason, nearly all conductivity meters simultaneously measure the conductivity and the temperature.”