Just to clarify (or maybe muddy
) the waters a little more...
There are essentially 4 versions of the Vantage Pro 2: wired and wireless, and with solar and UV sensors (Pro 2 Plus) and without.
The wired version is NOT expandable to extra stations. The wireless version can receive data from a mix of up to 7 extra wireless stations comprised of temperature only, temperature/humidity, and soil moisture/leaf wetness/temperature.
And, while you can add the solar/UV sensors to either Pro station at a later date, it's MUCH cheaper to order the Plus version up front if you think you'll want them.
And check out Rob at rainmanweather.com for pricing, too.