The Difference Between "から" and "ので"

今日は、天気がいいから外出しようと思う。 The weather is good today, so I want to go out.

今日は、天気がいいので外出しようと思う。 The weather is good today, so I want to go out.

Both of these sentences are correct, but awareness of cause and effect is a bit stronger in the first sentence than in the second one. This difference matters when you write a diary.

今日は母が来るから、朝、部屋に花を飾った。 (Slightly weird) Because my mother was coming, I decorated my room with flowers this morning.

今日は母が来るので、朝、部屋に花を飾った。 (Perfect) Because my mother was coming, I decorated my room with flowers this morning.

If you wrote the first sentence in your diary, it would seem a bit strange.　This is because we Japanese unconsciously think that awareness of cause and effect should be weak in written statements about your daily life. I suspect that many Japanese learners have had their "から-conjunction sentences" corrected to "ので-conjunction sentences" for this reason.

Taro: なぜ、花を買うの？ Why are you buying flowers?

Hiroko: 今日は母が来るから、部屋に花を飾るのよ。 (Perfect) I want to decorate my room with flowers because my mother is coming for a visit.

The above conversational sentences are perfect. Since the subject of their conversation is related to cause and effect, "から" is suitable. In this case, "から" is the better choice than "ので."