Column headings used in the observations data tables

Standard parameters

Temp/DewPt ( deg C )
Air temperature measured in the shade both from the sun and from the nighttime clear sky.
Dew point temperature (always less than Temp) is the temperature at which fog or dew forms (100% relative humidity) when air is cooled.

rh ( % )
Relative humidity. The percentage moisture compared to saturation.

Wnd/Gst ( km/hr )
Winds are measured at 10 metres above ground in an open area away from buildings or trees.
The MSC automated station wind is a 2 minute average, the gust is a maximum over 10 minutes.
The direction is reported to the degree but simplified here to 16 compass points: N, NNE, NE, ENE, E...

MSLP ( millibars; 1000 mb = 100 kPa)
Mean sea level pressure is the pressure at the station adjusted down to what would be sea level. The station's recent temperature is used to calculate the weight of a hypothetical column of air below the station to sea level. The weight (per unit area) is added to the station pressure to estimate the MSLP. If you have a barometer at home you might want to calibrate it to a nearby weather station reporting MSLP. That way your readings will make sense when comparing them to general weather information.

Precipitation

R1hr/R10m ( mm )
One hour or 10 minute rain total often measured using a tipping bucket rain gauge. This should read zero if the temperature is below zero. "rain" may be recorded when the temperature rises above freezing and any snow sitting on the instrument melts.

SDpt ( cm )
Snow depth is measured by an acoustic device pointing down at the snow.

S1hr (cm)
A one hour snowfall rate (S1hr) estimated from the SDpt.

Pwt (mm) A precipitation gauge measures the total weight of rain or snow and reports it in millimetres as if it's all water. The weight rises until the accumulated water is dumped and the instrument is reset to a lower value. SWEQ (mm)
Snow Water EQuivalent measures the snowpack by weight on a 'snow pillow'. The weight of snow on a platform is reported as if it is a depth of water in mm. Snow pillows are used in BC and Newfoundland. The instrument will show the gradual accumulation of snow in the fall and winter and the melt through the spring.

P1hr/p10m (mm)
A one hour or 10 minute precipitation rate estimated from Pwt (which may or may not be reported).

Manned and automated stations at airports

Manned and automated Nav Canada stations at airports also report weather, cloud, visibility and observer comments.

wx "weather", for example fog, rain, snow, etc., either manually or with instruments, sometimes both.

Here are the most common abbreviations used on this site:
NOWX no weather, maybe cloud
BR fog, (for fr. brume)
RN rain, add --/-/+ for very light/light/heavy, moderate rain is 2.6-7.6 mm/hr
SN snow, add --/-/+ for very light/light/heavy, moderate snow has visibility of .05 to 1 km
DZ drizzle
IP ice pellets
SG snow grains (small round flakes that bounce when then hit a hard surface)
TS or TRW thunderstorm
Add 'FZ' for freezing eg. FZDZ for freezing drizzle
Add a 'W' for showers eg. SW for snow showers/flurries
Add a 'BL' for blowing eg. BLSN for blowing snow

Visi visibility in km

Cld Cloud cover in percent of the sky.

COp Cloud opacity percent of the sky.

Rmk Remarks, often of convective cloud or distant showers.

For excrutiating detail see the weather glossary

Buoys

Weather buoys report wind, temperature and pressure much like ground stations but generally not humidity or precipitation. They also report sea state by measuring the motion of the buoy as waves go by, like a fitness step tracker for the ocean. EC/MSC buoys

WvHt ( metres )
Significant wave height. This is used in marine forecasts.

WvPd ( seconds )
Significant wave period

PkWH ( metres )
Peak wave height

PkWP ( seconds )
Peak wave period

SST ( deg C )
Sea Surface Temperature

Light stations

Lighthouse staff provide manned weather and sea state observations every 3 hours except overnight.

Visi (km)
Visibility

Wx (km)
Current weather including fog using abbreviations similar to those used in the manned airport observations.

Seas
Sea state. A visual description, for example rippled, chop, moderate or rough.

SwlDir (km)
Swell direction.

WvHt (metres)
Wave height, a visual estimate.

Rmk Remarks include comments on the wind and weather and occasionally the local sea water temperature 'SWT' in degrees C.

Hydrometric stations

WLevel ( metres )
Water level

WFlow ( cubic metres/second )
Water flow rate