I realize that this isn't scraperwiki, but BeautifulSoup, check it out anyways.
html = r"""<div id="karte_data_aktuelle_temperatur___CHA" class="karte_text_hidden">
<span style="font-size: 10px;">9.0</span>
<br/>
</div>"""
from bs4 import BeautifulSoup
soup = BeautifulSoup(html)
elem = soup.find('div')
print elem['id'], 'is the id'
print elem.text, 'is the value' #9.0