What is 花見 in English?

Some English speakers in Japan will say that 花見 means "flower viewing" but this is not so useful when speaking in natural English. 花見 is an event, you are not only looking at flowers! I can't ever imagine a native English speaker telling friends in his/her home country: 
"I went flower viewing last weekend."

"Flower viewing" is not natural English...
During cherry blossom season you may go to a 花見パーティー. What do you do at a 花見パーティー? You sit on a blanket outside, eat and drink. In English this is a Picnic! You had a picnic! Now let's add more information. Where do you have a 花見パーティー (picnic)?

You have a picnic under the blossoming cherry trees!

This is flower viewing (looking at flowers)

This is 花見 (having a picnic under the cherry blossoms)

So flower viewing is a direct translation but it is not exactly  花見! Next time you can tell your English speaking friends that you “Had a picnic under the cherry blossoms!” Enjoy 花見!!!