COMMENTS FROM THE AUTHOR:
The following Javascript program is freely available for use by any non-commerial fire-related department, organisation or individual.

The following Javascript Exercise has been tested BUT no guarantees regarding the accuracy of the calculations are made. If there are any errors let me know.

Calculating the Keetch–Byram Drought Index

All units are Metric!
ENTER THE COEFFICENTS IN APPROPRIATE BOXES
Yesterday's maximum screen temp
(°C)
Site's average annual rainfall
(mm)
Gross 24hr rain to 9.00am
(mm)
KBDI yesterday

Todays KBDI