Do you use an outdoor sensor and if so is it good, preferably ZigBee? So far I've found:
Mine are all indoor sensors, but a quick word of advice: Your starting point should be figuring out which of those devices are supported by whichever Zigbee integration you 're using.
Not much use if your outdoor sensor works but can't be integrated into HA. You'll end up having to create custom quirks for the device, & it's not an easy job for someone who's just starting out.
Thanks for pointing that out.
When posting this I hadn't realised that the SONOFF sensor - which I already have - is suitable being IP65.
They've just dropped the price so I've ordered eight of them.
Not sure why they would classify it as IP65 (which should withstand water from any direction), then say it's not suited for outdoor rain in the product page 
:
I have a feeling this is more meant for bathrooms where high humidity is an issue, but if you already have one and you're happy with it enough to get 8 more, then I hope I'm wrong.
Most should be fine if placed under a cover like just under a roof awning as the ratings are more for being under constant heavy rain and weather elements.
The other option is to just keep the main part of the setup indoors and put a probe via wire outdoors.
Maybe it's about getting reliable readings because you won't get that if it is soaked by rain or submerged in the pond! I'd already begun wondering how best to shield it without creating a micro climate around it. I later realised that's the idea of the B3D which is an enclosure not a sensor, but that's one big ugly thing that won't pass my filters let alone my wife's!
Even sheltered, but close to a damp wall might not be accurate as the purpose is to assess the causes of damp inside the building by comparing the outer and under readings. Only one of planned for outside at this point.
Does anyone have experience with outdoor Humidity sensors to share?
IP65 doesn't include submerging.
You can place IP65 device under direct rain but you can't place it in flood-prone areas or where water can collect
They likely recommended not to place it under rain either for their ignorance or to prevent complains from ignorant users.
Check out Ecowitt.
I have two outdoor temperature sensors that are part of a Z-Wave motion sensor, two DHT11's (not recommended) on Tasmotized ESP-01's indoor. In addition I have several not connected thermometers. My experience can be summed up as: "A person with one temperature sensor knows what the temperature is. A person with two, does not."
I was considering lining all ten up to see the variance but perhaps I should keep them apart. I don't like arguments 
Their Arithmetic can be mean.
I bought 3 indoor Sonoff temperature sensors, you can calibrate them with an offset to get them all matching closely. I set mine up against a known good reference and they track within 0.1-0.2deg of each other.
For outdoors I have an Aqara WSDCGQ11LM as it also does air pressure. I plan on getting the B3D enclousure for it, they are not that big, 10cm. All B3D is supply indoor sensors from Sonoffo or Aqara in them, they'll also supply the enclosure seperately.
Looks nice but it "Requires Aqara Hub (not 3rd-Party)" and I don't want to get that and an enclosure just to add atmospheric pressure.
AFAIK it works with 'any' zigbee coordinator.
Aqara say different, but if people can confirm this I might give it a go.
Here's the product listing on the Aqara website which says this. Their "but now" link goes to their listing on Amazon where I got the quoted text.
Isn't that what many constructors say to make you buy their stuff.
I could be wrong but maybe someone else can confirm.
Google says " Aqara WSDCGQ11LM, compatible with which zigbee controller ? "
I have 8 of those, even tried them in fridge and freezer
Have them in Aqara m2 via Native Matter Integration ( no airpressure entities there thou ) were previously in the "old" Homekit-Devices , where the airpressure was exposed
Ignore what it says on the product page. That's for people who don't use HA.
In case you're still doubtful, I had 2 of them on both ZHA & Z2M. They'll work with any supported zigbee coordinator
I don't get this whole thread... If one wants accurate outdoor humidity and temperature readings then just get a personal weather station. You won't have to worry about protecting it... because it's designed for the purpose of being outdoors.
I use a Tempest Weather Flow and it integrates nicely with HA.