I was watching a news broadcast on YouTube and when it moved over to the weather report, I noticed that 「今日の天気」was actually written as 「きょうの天気」. Also 「明日の天気」was also written as 「あすの天気」. It wasn't just the weather report but some other parts of the programme such as the main stream headlines, 「きのう」.
Why are these sentences or should I say, just the start of the sentence written in ひらがな and not full 漢字? Does it depend on the news programme? I asked my Japanese friend and he said he didn't know or even realise it.
For reference, I was watching おはよう北海道 (16:15) when I first noticed it.