If
P(down | rainy days ) = 1,
and
P(down | Mondays ) = 1,
then
P(down | rainy days ∩ Mondays) = 1
P(down | rainy days ) = 1,
and
P(down | Mondays ) = 1,
then
P(down | rainy days ∩ Mondays) = 1
This is a niche tweet in multiple ways.