The Weather Station V2.0 board have 5 additional ports to hook up more weather sensors.The following additional sensors can easily hooked up :

1. GY-1145 Sensor: for measuring UV Index

The SI1145 is a sensor with a calibrated UV sensing element that can calculate UV Index. It  can communicate via I2C communication (address 0x60).You can hook up this sensor with I2C port in the board which is located just side to the power switch.

You can read this article to know more about this sensor.

2. HDC1080: for measuring temperature and humidity

The HDC1080 is a digital humidity sensor with integrated temperature sensor that provides excellent measurement accuracy at very low  power. It can also communicate via I2C communication.

You can read this articleto know more about this sensor.

3. DS18B20: for measuring temperature

It can measure temperature with a minimal amount of hardware and wiring. These sensors use a digital protocol to send accurate temperature readings directly to your development board without the need of an analog to digital converter or other extra hardware. It uses one-wire protocol to communicate with microcontroller. It can be hook up in port-P2 in the board which is located on the right side of the Wemos board.

You can read this article to know more about this sensor.