BeautifulSoup is your friend.
import urllib2
try:
from bs4 import BeautifulStoneSoup #Using bs4
except ImportError:
from BeautifulSoup import BeautifulStoneSoup #Using bs3
url="https://api.projectnimbus.org/neaodataservice.svc/NowcastSet"
request = urllib2.Request(url)
request.add_header("accept", "*/*")
request.add_header('AccountKey', "OSJeROQjTg4v7Ec3kiecjw==")
request.add_header('UniqueUserID', "00000000000000000000000000000001")
result = urllib2.urlopen(request)
xml_str = result.read()
soup = BeautifulStoneSoup(xml_str)
prop_list = []
for content in soup.findAll("m:properties")
props = {}
for prop in content.findChildren():
props[prop.name[2:]] = prop.text
prop_list.append(props)
print prop_list