Weather Terms

Mean Temperature

The weather instrument takes a measurement every 30 minutes.  The mean temperature is the average of these readings from midnight to midnight.

Click the Back button to return to the weather page.


High Temperature & Time

The weather instrument takes a measurement every 30 minutes.  The high temperature is the highest of these readings from midnight to midnight.  The high temperature time is when the high temperature was reached.

Click the Back button to return to the weather page.


Low Temperature & Time

The weather instrument takes a measurement every 30 minutes.  The low temperature is the lowest of these readings from midnight to midnight.  The low temperature time is when the low temperature was reached.

Click the Back button to return to the weather page.


Degree-Days (Heating/Cooling Cost)

Degree-Day, unit used in estimating heat requirements in buildings and fuel costs.  The degree-day is based on the Fahrenheit temperature scale and is essentially a measurement of the difference between a standard indoor temperature and the (lower) outside temperature.  One degree-day corresponds to a difference of 1° F between the outside mean temperature and a given reference temperature, which is taken as 65° F for heating calculations.  Hence, one winter day with a minimum temperature of 30° F and a maximum temperature of 50° F, or a mean temperature of 40° F, would count as 25 degree-days.  For a given building, annual heating costs are directly proportional to the total number of degree-days in the year.  New York City has about 5300 degree-days during the total heating season; Chicago has about 6300 and New Orleans, Louisiana, only 1200.  Degree-days are also sometimes used to evaluate air-conditioning costs.  Here the cooling degree-day is used with mean temperature above, rather than below, a reference temperature of 75° F to determine cooling loads.

"Degree-Day," Microsoft® Encarta® Online Encyclopedia 2000 © 1997-2000 Microsoft Corporation.  All rights reserved.

Click the Back button to return to the weather page.

Degree-Days (Agricultural)

Because temperature plays an important part in the rate of development of plants and many pests (especially insects), a measurement which takes into account the accumulation of heat with passing time is necessary to predict maturation.  Degree-days provide a measure for calculating the effect of temperature on the development of plants and/or pests.  One degree-day is the amount of heat that accumulates when the temperature remains one degree above the base developmental threshold for 24 hours.  One degree-day is also the amount of heat which accumulates when the temperature remains 24 degrees above the base threshold for 1 hour.

Unlike strict time predictions of plant/pest development, degree-day predictions hold true regardless of location or temperature fluctuations.  As long as you know the number of degree-days necessary for plant/pest development, you may use degree-days as an accurate predictor.  For example, you may know that it takes, in general, three weeks for a specific pest to develop.  What you will find, however, is that the pest may take 4 weeks to develop in cooler weather and only 2 weeks to develop in warmer weather.  The time prediction can be off by up to a week in this example, while the degree-day prediction should result in far greater accuracy.

Click the Back button to return to the weather page.


Precipitation

The Precipitation figure represents the amount of liquid precipitation in inches.  Note: When snow is measured it is likely understated since the device was not designed to measure melted snow.

Click the Back button to return to the weather page.


Wind Speed, Peak, and Time

The weather instrument takes a measurement every 30 minutes.  The wind speed is the average of these readings from midnight to midnight.  Wind peak is the highest of those readings and wind peak time is the time that the highest reading occurred.

Click the Back button to return to the weather page.


Wind Dominant Direction

The weather instrument takes a measurement every 30 minutes.  The wind dominant direction indicates the direction the wind came from most of the time.

Click the Back button to return to the weather page.