Weather values are instantaneous:
#CFHT/GEMINI Weather Tower Data
2009/01/09 03:46:29 #Date/time of acquisition
WS=   16.94   #Wind speed (knots)
WD=  136.08   #Wind direction (degrees) (0-360)
T =    0.77   #Temperature (degrees celsius)
RH=   11.62   #Relative humidity
BP=  612.88   #Barometric pressure (millibars)