I assume you want to be able to monitor the temp on a smartphone or tablet remotely via WiFi. Otherwise, there are many cheap wireless RF thermometers with a dedicated transmitter & receiver such as these products from La Crosse:
The solution to your problem depends on your budget and the type of weather data you want to monitor.
This may be overkill for what you want to do but I'm a weather watcher. Years ago, invested in a Davis Instruments Vantage Pro 2 weather station:
I have the station mounted on a hilltop on my property, 1/4 mile from the house. The station relays weather data via RF wireless to receiver consoles in various rooms of the house.
I have remote temp sensors located at various locations, including the barns, and all the information is viewable on the consoles. Davis Instruments also has a WiFi app which allows weather information to be viewed on any smartphone or WiFi enabled device. The temp sensors have a range of 1/4 mile or so depending on obstructions. Repeaters are available and can be used to extend the signal to any range.
I'm sure there are cheaper solutions that will do what you want. Perhaps someone else can propose a product that will suit your needs & budget.