PH and temp

Temps do affect pH but it shouldn't be that much. Water at 7 pH will have a pH of 6.14 at boiling temperatures. I would take a small sample into a warmer area and retest the pH. Most meters compensate for temp as well, so if it gives you a temperature, it probably automatically compensates. Shake up your solution very well before taking a sample. Low temps could have caused some kind of separation within the solution.