This report shows modeled maximal temperatures on Mars according to latitude:

Title: On the possibility of liquid water on present-day Mars.
Journal: Journal of Geophysical Research, Volume 106, Issue E10, p. 23317-23326 (JGR Homepage)
Publication Date: 10/2001
http://www.agu.org/pubs/crossref/2001/2000JE001360.shtml

It appears in Fig. 4 on page 23,231. The maximal temperature at 70 degrees North latitude is given as 250 C.
This is below the freezing point of pure water but is in the range for liquid water brines:

Making a Splash on Mars.
"On a planet that's colder than Antarctica and where water boils at ten degrees above freezing, how could liquid water ever exist? Scientists say a dash of salt might help."
...
"One thing we have to be careful of is our everyday experience that
water always freezes at zero degrees," noted Hoover. "It doesn't.
Water containing dissolved salts freezes at a significantly lower
temperature. Don Juan Pond in Antarctica is a good example. It's a
high salinity pond with liquid water at temperatures as low as -24 °
C."
http://science.msfc.nasa.gov/headlines/y2000/ast29jun_1m.htm

Some images of Don Juan Pond:

Some reports argue there is no life in Don Juan Pond but this article discusses life on its periphery:

An extraterrestrial habitat on Earth: the algal mat of Don Juan [correction of Jaun] Pond.
Adv Space Res. 1983; vol. 3, 8:39-42.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11542753

Bob Clark