Evenin' all, this evening I've had 7hrs of dead calm conditions and have noticed that my screen thermo is lagging behind a 'control' thermo I have on a north facing wall by some distance since the cloud arrived - a short while ago the screen was at 0.4 c while the wall mounted thermo had climbed to 2.2. Usually the two are reasonably close. I always thought that fans were only needed in screens in the summer - but now think one would help in winter. Anyone else experience this?