Synthesizes extreme, but statistically possible, hot, cold or average sequences of hourly weather data for periods of up to one week for a specified month and for 329 locations in North America, with the capability of modifying or expanding the data for greater flexibility. Such data are needed in the design of building heating and cooling systems, particularly systems which utilize some form of energy storage. Screen Shots


extreme weather, weather sequences, simulation, energy calculation



Expertise Required

Student or engineer of HVAC system design. Low level of computer literacy required.


Worldwide distribution. Useful for U.S. and Canada locations


Researchers, Students, Engineers and Architects


All of the information required by the weather sequence generator algorithms is presented in the Input Window dialog box. The information is divided into the following six groups.

  • Location Information
  • Sequence Information
  • Drybulb
  • Humidity Ratio
  • Clearness Index
  • Wind


Generated weather data are displayed in the Table Window. A separate column is provided for each variable selected in the Display Variables dialog window. Each row in the table provides data for one hour. The number of hours of generated data is controlled by the number of days for the sequence that is entered in the Input Window. The data in the Table Window can be printed using the Print command. These data can also be selected and copied to another application using the Select All and Copy commands. The New Plot command can be used to plot any of the weather variables as a function of time. The generated data seen in the table can also be exported in either TMY2 or WYEC2 format using the Export Generated Data command. There is only one Table Window. A new table is created each time a new weather data sequence is generated. Hourly values of the generated weather variables appear in the Table Window. Any of the weather variables in the table can be plotted versus time using the New Plot command. The characteristics of an existing plot can be changed using the Modify Plot command. A plot can be printed using the Print command or copied to the clipboard with the Copy command. There may be up to five plots at any time. Use the Delete Plot command to remove plots if there are already five plots and additional plots are desired.

Computer Platform

Windows-based computer with CD drive and minimum 16 MB of memory. The program is designed for Windows 95, 98, or NT 3.51/4.0 operating systems. It will not work under Windows 3.X or on UNIX or Macintosh operating systems. PC-compatible only; not intended for network installation.

Programming Language

FORTRAN source code for the EXTREMES.DLL code is in EXTREMES.FOR. The source code is provided in an ASCII file that can be read in any operating system.


The EXTREMES menu driven program easily generates statistically possible weather data extremes. Unit system can be set for either SI or IP units.


Locations only consist of cities in the United States (Incl. Hawaii and Alaska), Canada, and various territories of the United States (Puerto Rico, Wake Island, etc.)





1791 Tullie Circle, NE
Atlanta, Georgia 30329
United States


+1 (800) 527-4723 US/CAN +1 (404) 636-8400


+1 (404) 321-5478






ASHRAE's Extremes CD-ROM is available for $99 ($79 for members of ASHRAE). Order on the web at www.ashrae.org/bookstore/bookstore.html. Order by phone by calling ASHRAE Customer Service at 1-800-527-4723 in the U.S. and Canada, or at (404) 636-8400 worldwide. Fax your order to (404) 321-5478. Questions about this or other ASHRAE products should be e-mailed to orders@ashrae.org.