airconditioner - an appliance that cools down the air in a room. 

avalanche - a dangerous slide of snow down a mountain.  E.g.  The skiers are warned about a possible avalanche.

blizzard - a storm with lots of snow and wind.  E.g.  The school is closed because of the blizzard.

breeze - light wind.  E.g. The ocean breeze is very soothing.

drizzling - raining slightly.  E.g. It is only drizzling.  I think I can still take the dog for a walk.

drought - a long period with no rain.  E.g. Forest fires are a serious danger during a drought.

flood - overflow of rain water.  E.g. The flood was so bad, our basement was full of water.

flurries - very light snowfall

fog - thick water vapor that blocks one's vision.  E.g. It is so foggy outside.  I can't see anything.

forecast - expected weather for the future

frost - ice crystals on a frozen surface

hail - small pieces of ice that fall during a storm

heat stroke - a flu-like condition a person can acquire after spending too long in the sun and heat.

heat-wave - extremely hot weather that lasts a short time.

humidex - short for humidity index.  It is an index number used by Canadian meteorologists to describe how hot the weather feels to the average person, by combining the effect of heat and humidity.  E.g. It is 30 degrees, but the humidex is 36.

hurricane - a tropical storm with strong winds and rain.  A hurricane is the same as a typhoon.  In the Atlantic and Northeast Pacific, the term "hurricane" is used.

meteorologist - a person who studies weather patterns.

overcast - no sun is visible. E.g. The sky is overcast this morning, but it will become sunny this afternoon.

precipitation - rain or snow that falls on an area. E.g. There is very little precipitation in the desert.

shower - quick or light rainstorm.  E.g. According to the weather report, there will be a shower this afternoon, so bring an umbrella.

sleet - rain that freezes as it falls

smog - heavy dark cloud caused by pollution

tornado / cyclone - violently spinning windstorm

wind chill factor - when the wind makes it feel colder than the actual temperature.  E.g. It is minus 2 degrees now, but the wind chill factor is minus 10.