I just put the default values that where in the one site in the settings, and see what it does from there. before i add a link to the page. I keep an eye on the NWS fire information which they list the Keetch-Byram Drought Index, Which right now shows us in white that shows us < 300 after putting the default values of ffmc 85, dmc 2 and dc of 5 it now shows:
Yesterdays values
FFMC DMC DC ISI BUI FWI
85.0 2 5 0.0 0 0.0
Todays values
FFMC DMC DC ISI BUI FWI
84.3 2 9 2.0 3 0.7
so yesterdays values get set to the default.