One other thing.
If you apply carb heat and get all the symptoms of ice melting, such as an initial drop in RPM and then a gradual increase, leave the carb heat on, for at least 30 seconds, and possibly much more - a couple of minutes or so.
You've just melted a load of ice in your carb and turned it to water. You don't want it freezing again.
Mention has been made of the temperature range.
Adiabatic cooling of the air in the carb (the cooling effect of coming through the venturi) is generally about 2-3 °C., but can be up to 5 °C. Most of the cooling effect is from the latent heat of evaporation of the fuel, and this is about 15 °C. Therefore, the total temperature drop in the carb will be about 20 °C.
At (for the UK) medium-to-high OATs such as 20 °C, anything above low humidity will reach saturation at 0 °C. Air with a relative humidity of 25% at 20 °C, or 50% at 10 °C, will reach saturation at 0 °C.
Check the graph worrab posted on page 1 of this thread.
At this time of year, carb icing is much less likely to be encountered. However, it is a good habit to behave as if it is, and always check for carb icing in FREDA checks, always check the carb heat in your power checks and downwind/prelanding checks, and always apply carb heat on final approach, cancelling as you cross the fence committing to land.