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HOME > Expert Assessments > Degree Day Assessment

Click here for final cooling degree day statistics
for the 2004 season (May - September 2004)

Click here for final heating degree day statistics
for the 2003-2004 season (November 2003 - March 2004) [PDF version]

Click here for final cooling degree day statistics
for the 2003 season (May - September 2003) [PDF version]

Click here for a chart comparing area- and population-weighted 48-state average observed and normal CDD's for the 2003 season [PDF version]

Click here for final heating degree day statistics
for the 2002/03 season (November 2002 - March 2003) [PDF version]

Click here for a chart comparing area- and population-weighted 48-state average observed and normal HDD's for the 2002/03 season [PDF version]

Click here for final cooling degree day statistics
for the 2002 season (May - September 2002)

The CPC weekly Degree Day Assessment discusses the Heating Degree Day (HDD) or Cooling Degree Day (CDD) outlook for the coming week, and reviews temperature and degree day statistics for the past week and the heating season (November - March) or cooling season (May - September) to date. This Assessment can assist energy managers in anticipating and analyzing fuel demand, because degree days quantitatively reflect the public need for energy to heat and cool businesses and dwellings.

For any individual day, degree days indicate how far that day's average temperature departed from 65 degrees F. HDD's, which measure heating energy demand, indicate how far the average temperature fell below 65 degrees F (since cooler weather means more heating fuel demand). Similarly, CDD's, which measure cooling energy demand, indicate how far the temperature averaged above 65 degrees F. In both cases, smaller values represent less fuel demand, but values below 0 are set equal to 0, because energy demand cannot be negative. Furthermore, since energy demand is cumulative, degree day totals for periods exceeding 1 day are simply the sum of each individual day's degree day total. For example, if some location had a mean temperature of 60 degrees F on day 1 and 80 degrees F on day 2, there would be 5 HDD's for day 1 (65 minus 60) and 0 for day 2 (65 minus 80, set to 0 since degree days cannot be negative). For the day 1 + day 2 period, the HDD total would be 5 + 0 = 5. In contrast, there would be 0 CDD's for day 1 (60 minus 65, reset to 0), 15 CDD's for day 2 (80 minus 65), resulting in a 2-day CDD total of 0 + 15 = 15.

In this Assessment, degree day and temperature statistics are based on areally-averaged numbers for each of 102 climate regions of approximately equal area that cover the contiguous 48 states.

[NOTE:  HDD forecast statistics are not available for some areas because of data problems. These are indicated by gray shading on the maps showing U. S. Climate Region statistics. We are investigating this problem and hope to have it resolved soon. The Climate Prediction Center apologizes for any inconvenience this might cause.]

• Supplementary Information

Outlook Maps, Graphs, and Tables

The CPC produces U.S. outlook maps for degree days, departures from normal, and average temperature percentile; tables of population-weighted state, regional, and national averages by state; and probability of exceedence graphs.

• U.S. Degree Day Outlook Maps by U.S. Climate Regions Based on output statistics from the Medium Range Forecast Model (MRFMOS).

• 7-Day Total Degree Days - The sum of each day's degree day forecast in each of 102 climate regions that cover the contiguous 48 states.
• 7-Day Departures from Normal Degree Days - The amount by which the 7-day total for each climate region departs from the average degree day total for the same 7 days during 1990-1999. Negative numbers reflect less energy demand than normal.
• 7-Day Average Temperature Percentiles - Compares the anticipated 7-day average temperature for each climate region to the expected range of averages for the same 7 days, based on the 1990-1999 distribution of observations.

• State Degree Day Outlook Tables

• Heating Degree Days
• Cooling Degree Days
• Probability of Exceedence Graphs

Monitoring & Data

The CPC produces maps showing observed degree days, departures from normal, averaged temperature percentile, and winter energy savings based on temperature; and provides station and regional data.

• U.S. Degree Day Maps

• Last Week's Degree Day Statistics
• Season-to-Date
• HDD's for Full 2002-2003 Season (November - March) [PDF version]
• HDD's for Full 2001-2002 Season (November - March)
• HDD's for Full 2000-2001 Season (November - March)
• HDD's for Full 1999-2000 Season (November - March)
• CDD's for Full 2002 Season (May - September)

• Current Statistics (Projected and Observed) by Climate Region

• Degree Day and Temperature Anomalies/Percentiles (HTML)
• Degree Day and Temperature Anomalies/Percentiles (ASCII)

• Current Statistics (Observed) by State

• Degree Day Deviations from Normal

• Forecast Verifications

Maps comparing forecast and observed degree day statistics

• January 17 - 23, 2005 HDD
• December 14 - 20, 2004 HDD
• December 7 - 13, 2004 HDD
• November 30 - December 6, 2004 HDD
• November 23 - 29, 2004 HDD
• November 16 - 22, 2004 HDD
• November 9 - 15, 2004 HDD
• September 14 - 20, 2004 CDD
• August 24 - 30, 2004 CDD
• August 17 - 23, 2004 CDD
• July 27 - August 2, 2004 CDD
• July 20 - 26, 2004 CDD
• July 13 - 19, 2004 CDD
• June 22 - 28, 2004 CDD
• June 15 - 21, 2004 CDD
• June 8 - 14, 2004 CDD
• June 1 - 7, 2004 CDD
• May 18 - 24, 2004 CDD
• Mar. 24 - 30, 2004 HDD
• Feb. 17 - 23, 2004 HDD
• Feb. 10 - 16, 2004 HDD
• Feb. 3 - 9, 2004 HDD
• Jan. 27 - Feb. 2, 2004 HDD
• Jan. 20 - 26, 2004 HDD
• Dec. 22 - 28, 2003 HDD
• Dec. 8 - 14, 2003 HDD
• Dec. 1 - 7, 2003 HDD
• Nov. 17 - 23, 2003 HDD
• Nov. 10 - 16, 2003 HDD
• Sep. 15 - 21, 2003 CDD
• Sep. 8 - 14, 2003 CDD
• Sep. 1 - 7, 2003 CDD
• Aug. 18 - 24, 2003 CDD
• Aug. 11 - 17, 2003 CDD
• Aug. 4 - 10, 2003 CDD
• Jul. 28 - Aug. 3, 2003 CDD
• July 21 - 27, 2003 CDD
• July 14 - 20, 2003 CDD
• March 17 - 23, 2003 HDD
• March 10 - 16, 2003 HDD
• March 3 - 9, 2003 HDD
• February 24 - March 2, 2003 HDD
• February 3 - 9, 2003 HDD
• Jan. 27 - Feb. 2, 2003 HDD
• Jan. 14 - 20, 2003 HDD
• Jan. 7 - 13, 2003 HDD
• Dec. 23 - 30, 2002 HDD
• Dec. 16 - 22, 2002 HDD
• Dec. 9 - 15, 2002 HDD
• Dec. 2 - 8, 2002 HDD
• Nov. 25 - Dec. 1, 2002 HDD
• Nov. 18 - 24, 2002 HDD
• August 5 - 11, 2002 CDD
• May 21 - 27, 2002 CDD
• May 14 - 20, 2002 CDD
• March 24 - 30, 2002 HDD
• January 28 - February 3, 2002 HDD
• January 21 - 27, 2002 HDD
• January 14 - 20, 2002 HDD
• January 7 - 13, 2002 HDD
• December 31, 2001 - January 6, 2002 HDD
• December 3 - 9, 2001 HDD
• November 12 - 18, 2001 HDD
• November 5 - 11, 2001 HDD
• September 17 - 23, 2001 CDD
• September 10 - 16, 2001 CDD
• August 20 - 26, 2001 CDD
• July 30 - August 5, 2001 CDD
• July 23 - 29, 2001 CDD
• July 16 - 22, 2001 CDD
• June 11 - 17, 2001 CDD
• June 4 - 10, 2001 CDD
• May 28 - June 3, 2001 CDD
• May 21 - 27, 2001 CDD
• March 12 - 18, 2001 HDD
• March 5 - 11, 2001 HDD
• February 26 - March 4, 2001 HDD
• February 19 - 25, 2001 HDD
• January 22 - 28, 2001 HDD
• December 26, 2000 - January 1, 2001 HDD
• December 11 - 17, 2000 HDD
• December 4 - 10, 2000 HDD
• November 27 - December 3, 2000 HDD
• November 20 - 26, 2000 HDD
• November 13 - 19, 2000 HDD
• November 6 - 12, 2000 HDD
• October 23 - 29, 2000 CDD
• October 16 - 22, 2000 CDD
• Prior Verification Maps

NOAA/ National Weather Service National Centers for Environmental Prediction Climate Prediction Center 5200 Auth Road Camp Springs, Maryland 20746 Climate Prediction Center Web Team Page last modified: March 25, 2003

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