In the following sentence
ダーズリー一家【いっか】が目【め】を覚【さ】ますと、外【そと】はどんよりとした灰色【はいいろ】の空【そら】だった。
「と」is used in a place where I'd rather use 「とき」 or 「たら」. I know that 「と」is used for inevitable conditions like facts of nature but it doesn't fit that sentence.
Does particle 「と」has another meaning similar to 「とき」in the context of the above sentence? If so, is there a difference between the two?
Similarly「と」and 「たら」(I think the difference here would be 「と」being more formal than 「たら」).