In the weather forecast, we’ll have partly cloudy skies today with a high around 55. Tonight, mostly cloudy skies, with lows in the mid-30s. Tomorrow, overcast skies and light rain expected, with highs in the upper 40s. Right now, we have partly cloudy skies and 41 degrees.

blizzard: A winter storm with winds of 35 mph or more, lots of snow falling or blowing and visibility near zero.

Celsius (Centigrade): The temperature scale of the metric system, based on 0 degrees as freezing and 100 degrees as boiling (at sea level). To convert temperatures to Celsius, subtract 32 from the Fahrenheit reading, multiply by 5, then divide by 9. Unless your station insists on using Celsius readings along with Fahrenheit, don’t use Celsius. Americans have clearly shown that they neither understand nor care about Celsius readings. See also Fahrenheit.

chinook wind: A warm, dry wind occurring along the Rocky Mountains, sometimes reaching speeds of 100 mph.

climate: The average of weather conditions over time.

coastal waters: Waters within about 69 miles of the coast.

cold front: The leading edge of a cold air mass advancing on a warm air mass. In the summer, thunderstorms can form a squall line in front of the edge. In the winter the result is often a cold wave.

cyclone: A storm with strong winds rotating about a moving center of low atmospheric pressure. Not the same as tornado. See hurricane.

degree-day: An index that is used to determine the amount of heating or cooling required to maintain constant temperature. The calculation assumes no demand for heat or cooling when the mean daily temperature is 65 degrees. To determine heating degree days, subtract the mean temperature for the day from 65. If the high for a day is 56 degrees and the low 32 degrees, the mean is 44, resulting in 21 heat degree days. Cooling degree days also lead to a calculation of the energy required to maintain a comfortable indoor temperature—using the same formula except subtracting 65 from the mean temperature instead of the other way around.

dew point: The temperature at which the air is saturated with moisture and dew starts to form. When the dew point is below freezing, it’s called the frost point—and that’s what you’ll get.

drought: An abnormal dry period lasting long enough to have a serious impact on agriculture and water supply.

dust storm: Blowing dust of 30 mph or more with visibility one-half mile or less.

earthquake: Involves a shaking of the earth’s crust—the release of built-up stress caused by portions of the earth’s crust grinding against each other. Commonly measured on the Richter scale. Minor earthquakes occur frequently; a reading of about 2.0 on the Richter scale can be felt by people. Each full point increase represents a doubling of strength. There is no upper limit to the Richter scale, although the highest ever recorded is 8.9. Anything above about 4.5 can cause considerable damage. The Richter scale measures an earthquake’s strength. The less commonly used Mercalli scale measures the earthquake’s intensity in a given area. On a 1 to 12 scale, 1 means hardly felt, and 12 means total damage.

El Niño: A warming of the tropical Pacific Ocean—starting along the coasts of Peru and Ecuador—that can cause disruption in the world’s weather systems. Major El Niño events occur every 5 to 10 years.

equinox: When the sun is directly over the equator. The autumnal equinox is usually September 23 (sometimes the 22nd); the vernal equinox is usually on March 21 (sometimes the 20th). The astronomic starts of fall and spring.

Fahrenheit: The temperature scale that is in common use in the United States. Freezing is 32 degrees; boiling is 212 degrees. In the unlikely event that you need to convert Fahrenheit to Celsius, subtract 32 from the Fahrenheit reading, then multiply by 5, then divide by 9. See also Celsius.

flash flood: A sudden, violent flood, usually after heavy rains or considerable, rapid melting of snow.

flood: Streamflow in excess of a channel’s capacity. Remember that reporting how high a river or the water will crest is meaningless without some comparison—particularly height above flood stage.

fog: A stratus cloud with its base at ground level, reducing visibility to less than 0.62 mile (1 kilometer). Heavy fog means visibility is down to one-quarter mile (0.4 km) or less.

freeze: When the temperature remains below 32 degrees long enough to damage crops. Hard freeze and severe freeze are synonymous and mean that the freezing conditions are expected to last at least two days.

freezing drizzle, freezing rain: Both terms mean that the precipitation will freeze on contact with a cold object or the ground, resulting in a coat of ice called glaze. See ice storm.

frost: Normally, scattered light frost is the term used. It is the freezing of dew on the ground.

funnel cloud: A violent, rotating current of air that does not touch the ground. If and when it touches the ground, it becomes a tornado.

gale: Usually, gale force winds, meaning sustained wind speeds between 39 and 54 mph.

heat index: A calculation of what the combination of heat and humidity feels like. Given as a “temperature,” it’s based on the idea that when the humidity is high, the temperature feels even hotter than it is. Sometimes called the misery index.

heavy snow: Generally, 4 or more inches of snow within 12 hours or 6 or more inches of snow within 24 hours.

high winds: Generally, winds of 40 mph or more for at least an hour.

humidity: The amount of moisture in the air. Relative humidity (the term more commonly used in weather forecasts) is the amount of moisture in the air as a percentage of the amount of moisture that air of that temperature can hold.

hurricane, typhoon, cyclone: A tropical storm with a warm core and wind speeds of at least 74 mph. Hurricanes that drop below that wind speed are downgraded to tropical storms. Hurricanes start east of the international dateline; typhoons start on the west; cyclones occur in the Indian Ocean. Otherwise, all three are identical.

hurricane season: When hurricanes are most likely to take place. In the Atlantic, Caribbean and Gulf of Mexico, that’s June through November; in the eastern Pacific, it’s June through November 15; in the central Pacific, it’s June through October.

ice storm: When rain falls through a thin layer of below-freezing air at the earth’s surface, causing the rain to freeze on contact; glaze.

Indian summer: An unseasonably warm spell in October or November. Purists insist that you can’t have Indian summer until after a cold spell or frost.

jet stream: A narrow band of strong wind, normally six to nine miles up, that influences the development and path of weather conditions.

knot: Used for offshore wind speed and the speed of boats and ships. Because knot means one nautical mile (6,076.1 feet) per hour, it’s redundant to say knots per hour. To convert knots to approximate miles per hour, multiply knots by 1.15.

Northeaster: Strong, steady winds from the northeast—along with rain or snow—associated with a strong low pressure system moving northeast along the east coast of North America. Also called a Nor’easter.

offshore waters: Generally, from 69 to 288 miles off the coast.

relative humidity: See humidity.

sandstorm: Same as dust storm, but for sand: blowing sand of 30 mph or more with visibility one-half mile or less.

Santa Ana wind: A warm, dry wind blowing west into southern California from the high desert plateau to the east, associated with very high temperatures, dust storms and fires.

seasons: Meteorologically, spring is March, April and May; summer is June, July and August; fall is September, October and November; and winter is December, January and February.

severe blizzard: Same as blizzard but with higher winds (45 mph or more) and temperatures of 10 degrees or colder.

severe thunderstorm: Intense thunderstorms with high winds (58 mph or more), heavy rainfall, hail, flash floods and/or tornadoes.

sleet: Formed from the freezing of raindrops or refreezing of melted snow-flakes into ice pellets 5 mm or less in diameter.

smog: Commonly used to describe polluted air that reduces visibility, especially common over large cities.

snow avalanche bulletin: Issued by the U.S. Forest Service for appropriate areas of the western United States.

snow flurry: A light, on-and-off snow shower.

snow squall: A heavy but short snow shower.

solstice: The summer solstice usually occurs on June 21 (sometimes the 22nd) when the sun is right over the Tropic of Cancer—the longest day of the year in the Northern Hemisphere and the astronomical start of summer. The winter solstice is usually on December 22 (sometimes the 21st), when the sun is over the Tropic of Capricorn—the shortest day in the Northern Hemisphere and the astronomical start of winter.

squall: A sudden increase of wind speed by at least 16 knots and lasting at least one minute.

stockman’s advisory: Public alert that livestock may require protection because of a combination of cold, wet and windy weather.

tidal wave: Popularly used to describe an unusually large and destructive wave that reaches land.

tornado: The most destructive of all atmospheric phenomena—a violent rotating column of air that forms a funnel and touches the ground. Not the same as cyclone.

travelers’ advisory: Alert that difficult road or driving conditions exist over a specified area.

tropical depression: A tropical cyclone with surface wind speed of 38 mph or less.

tropical storm: A warm-core cyclone with sustained wind speeds from 39 to 73 mph. See hurricane.

tsunami: A seismic sea wave, generally caused by an underwater earthquake.

typhoon: See hurricane.

urban heat island: The higher temperatures in urban areas caused by the burning of fossil fuels and the absorption of heat by pavement and buildings.

UV (ultraviolet) index: An index that measures the exposure to ultraviolet rays on a scale of 0 (least exposure) to 15 (extremely high exposure).

warm front: A front created by warm air moving into an area with colder air.

warning: Generally means the existence or suspected existence of whatever the condition is that’s being warned about.

watch: Generally means the possibility of or correct conditions for whatever is to be watched.

wind chill: A calculation of what the combination of temperature and wind feels like on exposed skin. The lower the temperature and/or the higher the wind, the larger the wind chill factor or index—and the more miserable and cold we feel.

Boston beat Baltimore 5-to-2 … Cleveland over Toronto 7-to-4 … New York edged Oakland 2-to-1 … and Detroit shut out Minnesota 3-to-nothing.

Dallas trounced Green Bay 13-to-10.