Ugly truth
Cold-weather burn
The set point on the controller is the box temperature, not the work the fire is doing. In January the fire is also heating the air that keeps leaking out.
People post a 12 lb brisket at 225 F and wonder why a hopper that lasted all night in May died at 2 a.m. in January. The meat did not change. The delta-T did.
Thin-wall grills feel this first. A leaky lid, a warped gasket, or a wind corridor along the fence will add another multiplier the controller cannot see. Wet pellets make it worse because some of the fire's work is boiling water you already paid for.
What PelletDeck does with that
The calculator has an ambient toggle. Winter / sub-freezing is 2.1x the mild-weather pellet estimate. That is a planning multiplier, not a measurement of your patio. If you are on a ridge in 15 F wind, budget more.
Open a 12 lb brisket at 225 F in winter. Then flip the toggle back to mild and look at the hopper warning change.
Ops notes that are not magic
Keep a full hopper and a spare bag next to the grill, not in the garage after you go to bed.
Do not babysit with the lid. Every peek dumps heat you then have to buy again.
A welding blanket or a well-fitted cover designed for running cooks can help. A random tarp that melts or blocks the exhaust can hurt. Use judgment.
Read the formula page if you want the exact exponents. Read empty hopper overnight if the warning is already red.