A bearded dragon regulates its body temperature by moving between a hot basking spot and cooler ground, and digestion, appetite and immune health all ride on that gradient working. The enclosure you set up in spring does not stay correct by itself: the room around it changes with the seasons, and the dragon's temperatures change with it. Seasonal basking care is really the habit of re-measuring and re-balancing the same setup four times a year.
The Temperatures You Are Defending
The basking surface for an adult dragon wants to sit around 100 to 110 degrees Fahrenheit, measured on the surface itself with an infrared temperature gun — air temperature readings on the glass will mislead you. The cool end should fall to the low-to-mid eighties so the dragon can genuinely cool down, and night temperatures can drop further without any heat source for a healthy adult in a normal home. Over the basking spot, a quality UVB tube spanning much of the enclosure length, mounted at the distance its maker specifies, gives the dragon the ultraviolet it needs exactly where it spends its warm hours. The thermostat controlling the basking lamp protects against the days the room does something unexpected.
Summer: Protecting the Cool End
Summer's problem is rarely the basking spot — it is the disappearance of the cool end. A hot room lifts the whole enclosure, the gradient flattens, and the dragon starts gaping, hiding or soaking because it cannot get cool enough. Ventilate the enclosure more freely, move it away from sunlit windows, and consider a lower-wattage basking lamp for the hottest months since the room is doing part of the lamp's work. Check that the basking surface has not crept above range even as you protect the cool side; both ends matter. Offer water for drinking and the occasional soak during heatwaves, and watch appetite — a dragon off its food in a heatwave is often simply too warm everywhere.
Winter: Holding the Hot Spot and Reading Brumation
Winter pulls the other way: the basking lamp works harder against a cold room and may no longer reach range at the old height, so raising the basking platform or fitting a higher-wattage lamp on the thermostat restores the spot. Shorter days are natural; keep a consistent light cycle rather than chasing the dark evenings, and replace the UVB tube on its maker's schedule regardless of season, since output fades whether or not the tube still glows. Winter is also brumation season for many adults — a healthy dragon may eat little and sleep for weeks, which is normal, but it should start the season at a good weight and still be offered water. A dragon losing obvious condition, or one that was unwell before slowing down, needs a vet rather than an assumption. Logging each season's temperature readings and lamp changes in KinsLe Care Teams builds the year-round picture that makes next year's adjustments obvious.