why is that?

[My favorite season is spring.] Why is that?

When we ask someone 'Why is that?' we want to know the reason for an answer or a statement they made.  It can basically be used the same way as 'Why?'  Notice the following:

1. "Really. Why is that?" Because I love to watch the flowers bloom.
   
2. "I don't want to go anywhere tonight." Why is that?
   

not so

In spring, it's not so cold but it's not so hot.

We use the phrase 'not so' to compare what we are talking about to something else.  We can replace this phrase with 'not too' in many situations to show that what we are talking about is between two known extremes.  Notice the following:

1. She's not so angry that she won't talk to you.
   
2. It's not so cold that you need a hat.
   

end of winter

Right now, it is the very end of winter.

The 'end of winter' is the final part of the season of winter, which comes between fall and spring and usually has colder weather.  Notice the following:

1. You must be very excited for the end of winter.
   
2. There is usually a lot of mud at the end of winter.
   

just starting

It is just starting to become spring.

If something is 'just starting' the action began very recently and is not completed yet.  Notice the following:

1. It was just starting to get dark when he left.
   
2. I was just starting to fall asleep when you called.
   

breezy

It's sunny, cool, and breezy.

When the weather is 'breezy' there is wind but it is not very strong.  It is a comfortable movement of the air outside.  Notice the following:

1. We sat on a comfortable, breezy beach and had a picnic lunch.
   
2. It is a little breezy outside so you may want to bring a jacket.