I've had this PWS for about 3 months now. For a while the outdoor temperature readings have been 2-6 degrees off whenever it got cold in my area (also hot too). All other readings seemed okay. After a bunch of experimenting over weeks I think I finally have been able to get accurate outside temp readings without even applying any calibration offset in the iOS app. In fact that offset isn't very good because if your temp is off, it will be off in a non-linear fashion with changing temps, so applying a hard offset won't really help.The outside module is so convenient to just place on top of a table or any hard surface without trying to mount it on an arm. Initially I had it placed on the edge of a patio to try to get it as close outside as I could but also keeping it away from sun and rain. But that gave incorrect readings. I think the issue is that whenever you have the module anywhere close to the home structure there must be some non-negligible heat radiation coming off the structure to influence the module significantly. I moved the module to the outer edge of my pool cage on a waist-high railing, which put it about 20 feet from the main house structure and now temp readings day and night are definitely in good agreement with surrounding stations and airport, maybe a 1 or 2 degree difference among some surrounding stations (looking at wunderground's map). Also, since its not mounted on an arm, I found placing it upside down so that the vent holes are not close to the surface it sits on helps too. There is also temperature influence with what it sits on.The only other main challenge now with its new position is ensuring sunlight never hits it directly. I think I have that resolved but its definitely something you will have to consider if you move it away from say a protective patio of your house. Also, while folks claim that the module should not be exposed to rain - I do not see that mentioned in the manual, only that it should not be in sunlight since it will absorb heat and throw off the temp reading. There are companies that sell solar radiation shields for PWS use as well, so that is always an option. I think Netatmo should sell that as an add-on.Hope these little findings of mine helps anyone that may have similar troubles. I must say that when I look at the wunderground map I see some station reporting temps that are outside the consensus of stations around it. I look at the hardware being used and it's been about 8/8 being a Netatmo PWS! This means that it is fairly common for folks not taking great care in the placement of the outdoor module but I don't really blame them, the documentation is severely lacking. The hardware is fine, I wish Netatmo would have basically provided the information I mentioned in this review in the manual. I had to figure it out myself over time. It is almost as if they don't really know their hardware very well because I have read some of the reviews on here reporting issues with the module and the suggestions given from Netatmo were a bit crazy. Have to dock a star for that.I love using Netatmo despite the documentation/tech support issue however. I've given new life to old iPhones and iPads being mounted weather info screens around the house. There is an SDK for those who are interested in having custom software interface with the hardware. My next task is to have some code which will acquire rain totals and use that to configure a sprinkler controller that is also internet connected. One practical use of having a PWS that is internet/intranet capable. If you are on the fence about buying this PWS I'd say to go ahead and get it once you give some thought to where you will position the outdoor module.