2 Types:
1: A hot, cloudless summer day ended with a gorgeous red sunset. A raging thunderstorm would start at about 22:00 untill 23:00, after wich the clouds clear away again and a beautifull night sky is revealed.
2: A mid-spring day, about 22 degrees, a light breeze carrying those sweet blossom fragrances and lots and lots of fluffy sheep cloud dotting the blue sky. It would end in a beautifull sunset and another brilliant night sky.
Both are incredibly romantic and overal happy scenario's. I'd spend the first one just baking in the sun (while reading, I love reading while sunbathing) and playing in the water with my girlfriend, followed by watching the thunderflashes and stars. I love watching thunder, sunsets and stars, it's awesome and can be incredibly romantic.
The second scenario is, again, a perfect one to spend with one's girlfriend. Just relaxing, laying in the grass side by side, under a tree in the shade, just watching the clouds drift by and recognising shapes together. Nothing to worry about, not a care in the world, just pure relaxation and eachothers company.
Both are already awesome alone, but are improved a thousandfold with your soulmate next to you.