Based on the wording of the violation notices above it seems the law allows the regulator/airport operator to use some discretion when determining whether a fine is to be imposed. It seems reasonable that weather delays are probably one of the criteria to be taken into consideration when making a determination.

this page has some info about the rule: flyreagan.com - DCA Reagan National - Nighttime Noise Rule
and here is some of the statutory authority: 49 USC Ch. 475: NOISE (house.gov)

neither of which seem to directly answer your question.