Varying Cooling on my Driver

Hi all.

Since it's started getting pretty cold I have noticed that the temp gauge on my Driver will vary from 3/4 up to 1/4 down depending on if I am sat in traffic or free flowing traffic.

The 3/4 up is how it has pretty much always been, but I've never had it go back down to 1/4 (just outside the first square block on the gauge..

Should I be worried? Could the air temp be interfering with my reading?

I've recently replaced the (leaking) water pump, flushed the whole system and topped up with coolant.

Have you got a summer thermostat? It's bloody cold out there at the moment. I have a winter one in and the temp guage stays still and the heater works a treat.