Seems, the only advice on Paessler KB for weather monitoring is to add some iFrame on a map. I wanna share my experience with "HTTP XML/REST Value" sensor.
Recently I found a post about Yandex.Weather providing its data in XML: http://habrahabr.ru/post/136149/
Mine solution was to add "HTTP XML/REST Value" sensor with URL: http://export.yandex.ru/weather-ng/forecasts/27612.xml and specify node "temperature"
City ID can be found here: (27612 was for Moscow) http://weather.yandex.ru/static/cities.xml
Everyone else now can easily google his own favorite weather provider's XML feed and parse it. PTF.XMLRestQB tool helped me to determine the right node: https://kb.paessler.com/en/topic/48783-is-there-a-tool-available-that-can-help-me-building-queries-for-the-xml-rest-sensor