How long are you going for, budget, airport you can fly from, when in March - 1st or 31st?

Short haul - Canaries, Madeira, possibly Cyprus
Medium haul - Egypt, Middle East, Gambia, Cape Verde
Long haul - Carribean, Florida, central/South America, South Africa, India, Far East, Australia

If you are considering the end of March don't rule out Southern Spain/North Africa.

most have been mentiond.. but to add southern Turkey around Antalia/Side area is quite warm

we,ve been to lanzarote last 2 years (15 march )- always been hot- hot enough to sunbathe and use the pool- does get a bit chilly on an evening- so take a cardy- We're off again this march- and woukdn't dream of going anywhere we wouldn't come home with a tan!!

belly

Egypt ..Red sea . Always my choice at that time of year .. Hot and sunny guaranteed ..temps around 30.

Another vote for one of the Red Sea Resorts, Sharm, Taba Heignts, Hurhgada etc Lovely sunbathing during the day, a bit cooler on an evening, but all you need is a light cardi and sometimes not even that.

Another vote for Egypt here, guaranteed lovely weather

We have been to Tunisia for the past 2 years in March and had lovely sunny weather.
Its cheaper to get to than Egypt but you are certain to get sunshine there.