I've been looking for a long time and finally found this thermometer/hygrometer that doesn't require a battery and is suitable for both indoor and outdoor use. There were two blocks in the package, I placed one next to the humidifier and the other on the door frame. So I know how much humidity a humidifier can increase (between 30% and 45%) and how it compares to outside. They work great and I'm not worried about cold weather draining the battery as they aren't needed.
Wintact Handheld Anemometer Water Resistant, Small Digital Wind Speed Meter Gauge, Pocket Air Flow Tester With Measuring Wind Temperature 14β To 113β For House HVAC Outdoor Kite Boat Sailing Surfing
14 Review
Precise Humidity Control With Xikar PuroTemp Round Digital Hygrometer, 10-Second Refresh Rate
27 Review
Room temperature and humidity sensor Aqara Temperature and Humidity Sensor
59 Review
Wintact Handheld Anemometer Small Digital Vane Wind Speed Meter Gauge, Pocket Air Flow Velocity Tester With Measuring Wind Temperature 14β To 113β For House HVAC Duct Outdoor Kite Boat Sailing Surfing
18 Review
ETL Listed VIVOHOME Portable Evaporative Air Cooler 110V 65W Fan Humidifier with LED Display, Remote Control, and Ice Box for Indoor Home Office Dorms
8 Review
π¬οΈ Evapolar EvaCHILL - Ultimate Personal Evaporative Air Cooler, Humidifier, Portable Air Conditioner & Fan in Urban Gray
3 Review
TOSOT 10000 BTU Portable Air Conditioner with Remote Control, Built-in Dehumidifier, Cooling Fan for Rooms up to 400 sq.ft, Grey
6 Review
π¬οΈ Stay Cool Anywhere with the Portable Air Conditioner Evaporative Air Cooler
9 Review