Wireless temperature sensor system using Bluetooth and a Particle Boron 2G/3G Kit.

[dreamER]

HI and welcome to the community !!!

here I found some interesting conversation which maybe will work for you:

BLE Beacon Thermometers

Hi @Circuitman , since I already made a suggestion this morning related to YoSmart devices, I’m feeling a bit like a “pusher”, but am doing it only because I’ve had success. YoSmart (YoLink) makes a temperature/humidity sensor that’s LoRa that might be worth considering. I’ve used these and “integrated” them with Particle devices via IFTTT and wonder if that might be something worth considering for your application.

also here is something which is worth to check as is pretty cheap and you can flash your own code on it:
Mijia Bluetooth Temperature/Humidity Sensor with LCD Display : ID 4881 : $9.95 : Adafruit Industries, Unique & fun DIY electronics and kits

Also not sure if you will be able to get range of 30m for BLE IMHO LoRa will be better option in this case.
Best,
Arek