Not to step on toes here, but in my opinion the acu-rite thermometers and hygrometers are junk. I know a lot of people on here use them, but I don't trust them and here is why. I have 4 of them and if I set all the probes side by side and all the displays side by side I get temp differences of up to +/- 5 degrees. As for the hygrometer part I was getting differences up to 20%.

I didn't like this so I went out and paid some big bucks on some Iso-9000 certified calibrated gear that actually comes with a certification in the box that gaurantees the calibration. From my testing the Acu-rite Hygrometers do not work, differences of up to 40% compared to my calibrated piece of equipment. The dial type may be off but I can mark them with a 50% reference and 70% reference using my calibrated piece of equipment and know when my humidity is within that range, below that range, or above that range. As for temps I can sort of use the Acu-rite as a reference as I document the temp it reads when my calibrated piece of equipment reads good, then I remove the calibrated piece and know then temps go up or down. If it goes up or down more than a degree without being disturbed I get the gun out and start checking!