First thing to do at the end of winter is swap the bottom boards. A simple task, just lift hive from existing base to the new clean base, then put it all back in place. Inspect what is on the bottom board you have just taken off. This is a good way to check without losing any heat out of the hive. Same with swapping over a lid, inspection of the old lid will show you any excess moisture, mould, burr comb etc.
I wouldn't go looking for brood disease at this stage as that is a longer inspection.
Check that they still have honey and maybe have honey coming in.
But before opening your hive observe what is happening, and I can't explain all the things that you can see happening it's you who must learn these things.
Eg is there pollen coming in, if so how many types (at least 1 is good, 3 is great).?
What is the source of the pollen?
Are the bees getting nectar from those pollen sources as well.
Are the bees all coming out of one side of the hive.?
In the arvo are there lots of bees flying out and just buzzing around a short distance from the hive?
Are these young bees or just bees on cleansing flights?
Are the bees cleaning out crumble from the bottom of the hive and throwing it out.
Etc etc etc... lots of things to know before opening a hive as these questions once answered give you reason and purpose for your inspection.
unless your just looking inside the hive just to make you feel better, then go for it full inspection.
Temperature. It's not what the top temperature is its how long in the day it's at those warmer Temps. Eg both melbourne and Mildura were say 18?c today. Mildura reached that temperature by about 11.00 am and was still about that hot at 5.00 pm .melbourne reached that temp at 2.30 pm and had started to cool down by 4.30. So a hive inspection in Melbourne at 2.00 pm would leave a cooled down brood nest and with a over night low of 6 ?c it would be hard for the bees to recover. Same hive inspection in Mildura at 12.00 would give the hive 4 hours of sunshine to reestablish a warm nest.
I know your not in those locations but I'm sure you know what I'm getting at. ( and I made those Temps up so don't anyone chip in with a comment on that ☺). Getting to know your local area you will learn to judge all these things. A hard way to learn is to see the bees removing dead brood out next week and then realizing it was you who chilled the brood. Beekeepers kill more bees than anything else.