Weather vs. climate
| Weather | Climate |
|---|---|
| Conditions right now or over a few days | Average conditions over many years (usually 30) |
| "It’s snowing today." | "Winnipeg has cold, snowy winters." |
| Changes quickly | Changes slowly |
A simple saying: "Climate is what you expect; weather is what you get."
Measuring weather
| Weather factor | Tool | Unit |
|---|---|---|
| Temperature | Thermometer | °C |
| Air pressure | Barometer | kilopascals (kPa) |
| Wind speed | Anemometer | km/h |
| Wind direction | Wind vane | N, S, E, W |
| Precipitation | Rain gauge | mm |
| Humidity | Hygrometer | % |
Air pressure
Air has weight. Air pressure is the push of the air above us.
- High pressure usually brings clear, sunny weather.
- Low pressure usually brings clouds, rain or snow.
A falling barometer often means a storm is coming.
The water cycle
The water cycle moves water around Earth over and over. It is powered by the Sun’s energy.
| Step | What happens |
|---|---|
| Evaporation | The Sun heats water in oceans, lakes and rivers. It turns into invisible water vapour and rises. |
| Transpiration | Plants release water vapour from their leaves. |
| Condensation | High in the sky, the air is cool. Water vapour condenses into tiny droplets that form clouds. |
| Precipitation | Droplets join and grow heavy. They fall as rain, snow, sleet or hail. |
| Collection | Water collects in oceans, lakes and rivers, or soaks into the ground as groundwater. Then it evaporates again. |
The water you drink today might once have been drunk by a dinosaur!
Clouds
| Cloud | Looks like | Weather |
|---|---|---|
| Cumulus | Puffy cotton balls | Fair weather |
| Stratus | Flat grey sheets | Overcast, drizzle |
| Cirrus | Thin wispy streaks high up | Fair, but change may be coming |
| Cumulonimbus | Tall towers with flat tops | Thunderstorms, heavy rain, hail |
Wind
Wind is moving air. It happens because the Sun heats Earth unevenly. Warm air rises, and cooler air rushes in to take its place. Near lakes and oceans, this creates sea breezes during the day.
Severe weather
- Thunderstorms: lightning, thunder, heavy rain. "When thunder roars, go indoors."
- Tornadoes: spinning columns of air touching the ground. Canada averages about 60 confirmed tornadoes a year.
- Hurricanes: huge spinning storms that form over warm oceans.
- Blizzards: strong winds with blowing snow.
What affects climate?
| Factor | Effect | Example |
|---|---|---|
| Latitude (distance from the equator) | Closer to the equator = warmer | Brazil is warmer than Canada |
| Nearness to water | Water keeps temperatures milder | Vancouver has milder winters than Calgary |
| Elevation | Higher = colder | Mountain tops have snow even in summer |
| Ocean currents | Warm currents bring warmer air | The Gulf Stream warms western Europe |
Climate zones
- Polar: very cold all year (the Arctic)
- Temperate: four distinct seasons (most of Canada)
- Tropical: hot and often wet all year (near the equator)
- Dry: little rain (deserts)
Common mistakes
- Using weather and climate as the same word.
- Thinking clouds are water vapour. They’re tiny liquid droplets or ice crystals.
- Thinking water is used up. It cycles again and again.
Try it yourself
- Put a little warm water in a clear bowl, cover it with plastic wrap, and put ice cubes on top. Watch the water cycle happen!
- Record the temperature, clouds and precipitation each day for a week.
- Compare the average January temperature of your town with a town near the equator.
Quick recap
- Weather is short-term; climate is the long-term average.
- Thermometers, barometers and rain gauges measure weather.
- The water cycle: evaporation, condensation, precipitation, collection.
- Different clouds signal different weather.
- Latitude, water, elevation and ocean currents affect climate.