Do all your phals spike at the same time?

[katrina]

Jkofferdahl is right about the temps. There are many spring/summer bloomers and since temps are on the rise during those seasons, it likely isn't lower night temps that triggers the spike. More likely an increase in daytime temps or "spring rains".

Once you've grown the phals for a couple of years you will begin to see a pattern. Even after a couple of years...you likely won't see specific times for flowering but rather "seasons".