Hi Moo
I would pack for all weathers if you aren't sure - better safe than sorry.
The good news is that there is plenty to do when the weather isn't so good.
Leisure services Sol Nessebar Palace All Inclusive
* Rose SPA Center with Whirlpool, Turkish steam bath, sauna, solarium and variety of body treatments and therapies.
* Outdoor/Indoor swimming pool.
* Fitness Hall
* Indoor billiards, table tennis, table football, darts
* Kids Club
* Children´s castle with 2 separate pools and water slides
* 3 outdoor floodlit tennis courts (green set)
* Volleyball, basketball, football, multipurpose playgrounds
* Green areas with chess, different types of cradles
* Water sports at the beach (catamarans, trimarans)
Facilities
* Souvenir/beach accessories shop
* Internet club
* Doctor on call 24 hours
* Patrolled Parking
* Currency exchange
* Laundry service
Here's the link to their website if you want to find out more.
http://www.solmelia.com/hotels/bulgaria/nessebar/sol-nessebar-palace-all-inclusive/home.htm
Kind regards
Olly, your editor