Bees into flow frames

Just wondering does anyone else find that the bees only go into the flow frames when you have some consecutive days of warm weather? I find that my bees would rather fill the outside frames of the brood box, before going up into the flow super. If the weather is like 25c every day they will move up into the flow super but if the weather is like 22 20,18,20,18,22 they would rather fill the brood box (I have 2) honey stores, causing a possible problem of becoming honey bound and possible swarming. I have now placed a normal honey super (8 frame) on top of the second brood box below the flow super, which I’m changing out frames as they fill the honey super then start filling the brood box before going into the flow super.
Any ideas ? its all good if you have constant days of 25c but at the moment, start of spring, some cold days (14c) some rain days, some great spring days(22c), really strong hive and nectar flow.