Both events are plausible i think, but what do you think is more likely here?
Bremerhaven sets a new record high for January with a temperature of 15.0°C/59.0°F- our record high for January so far is 13.1°C/55.4°F which was set just recently in 2005. Temperatures above 10°C/50°F are generally rare here during January, but in milder spells they can occur a few times, but in most cases a high of 11-12°C/52-54°F will be the limit.
Second option is a snowfall in May (which doesn't have to settle). As far as our records show, genuine snowfall has not occured yet in May since the records began in 1949, however sleet was observed on 8th May 1957, this was also the only May in history where a frost was recorded with a low of -1.1°C/30.0°F.
While i won't rule out a genuine snowfall at all in May, it must be a very rare event occuring maybe once in 80-100 years here, further away from the coast, snowfalls have been observed in May even sometimes in Late May.
Here are our climatological stats
http://en.wikipedia.org/wiki/Bremerhaven#Climate