The Rhododendron plants outside our bedroom window help us to tell how cold it is … today for example, overnight was cold; I took this picture about 7:30am when it was maybe 15f (-9c):
You can see how the Rhododendron has “dipped” it’s leaves nearly vertical, presumably as an adaptation to allow any falling snow to drop off the leaves and prevent breaking branches!
This afternoon, 3pm, the temperature is close to 40f (4c), and the Rhododendron has responded:
M&I / GBMINI 
I’ve never noticed that before. Who’s a clever clogs?
Actually, it’s Margaret who noticed it first, so it’s her 🙂