I researched London last night and found flight and hotels I wanted to stay at. I was ready to book until I checked the weather in London in April. Average temperature was around 30-50 degrees. And it rains average 15 days. Wife and I agreed that's too cold and wet for us. So I think London and Paris are out. Now, I'm thinking Rome due to the weather. But it's so confusing. The more I look, the more confused I get where I should go. Too many choices. I need to hurry up and decide before the cheap fares disappear.
To confuse the matter more, I just found some cheap fares to Aruba as well.
Central and northern europe (including northern Italy) is usually wetter in March and April and they're not dry areas in general, there's no way around that. The UK and Brittany & other places around there are the worst of the worst in this regard of course, they're rainy and mild year-round. Doesn't mean they're not worth visiting of course, on the contrary, they're different because of this, but if you're used to florida spring breaks maybe it's not what you're looking for.
The best you will get in central Europe is sunny-ish and mildly warm but humid sweaty weather, yet not warm or dry enough to be in a t-shirt.
I've been to Sicily twice in April and it's always been nice weather without too much rain (and especially no extended rainy/cloudy periods) and it's definitely warmer there. I even took a dip in the sea just for the sake of it but it was too cold to immerse fully, the air isn't really warm enough for it either (probably doable for northern germans but I'm not sure).
You could go there and rent a car and tour for a week. You'll mostly be visiting roman and greek historical sites and beautiful city centres (there's lots of baroque architecture in the south).
In april it's average min 10°C - average max 20°C.
Check out some pics of Modica Noto and Ragusa for the baroque stuff.
Villa del Casale in Piazza Armerina is a must-see, there's huge roman mosaics in it.
Ortigia is also beautiful.
As you see I've mostly visited the south of it, but if you arrive in Palermo it's a beautiful drive through the central part of the island, it's supergreen in April with beautiful sloping hills.
Big cities in southern italy generally aren't a quite as good experience for various reasons and I can't tell you much about it. I've been to Naples and the traffic for dinner time on the coast was very heavy.
Taormina is also nice but more busy with tourists (nowhere close to Prague or other big tourist destinations), the places I listed before were fairly empty instead. It has a pretty well-conserved greek theater though.
Sicily is also poorer than the rest of Italy so food is rather cheap and you will stuff your face with sicilian pastries.
Rome is warmer than northern Italy so if you want to visit a big city with lots of stuff it's an idea but I can't tell you anything about it.
Right now southern sicily is having problems with floods but these issues are only temporary and don't hit historical centres usually (villages built in non-proper places don't last long enough to become historical).
This winter is very weird, it's very sunny in the southern alps and the po valley but with icy nights which is unusual, while in the mountains of central Italy they're getting killed by metres of snow and earthquakes. There's a total lack of snow in the alps.
So it's hard to tell what you will find in April really. Holidays and weather are always a problem.
I was fooling around with Google Flights for random destinations and came across a place I've never heard of. Hurghada, Egypt. From Google images, the place looks beautiful. Airfare is only 46k points roundtrip on Turkish Air. Resort hotels at Hurghada are ridiculously cheap. The top luxury hotels on TripAdvisor are between $100-200 night and many luxury hotels are under $75 a night. Nice mid-range hotels are like $35-40 a night. Food and excursions are all super cheap by Western standards. There is Visa requirement to enter Egypt but it's only $25 per person and can be paid at the Egypt airport on arrival. The only thing I'm worried about is the potential for crazy terrorist attack. I think there was one back in December at one of the resort there and there's current travel advisory cautioning Americans from traveling to Egypt right now.
Better than sharm as it's not in the sinai but still not very safe and tourism has tanked as a result, that's why it's supercheap.
http://egypt.liveuamap.com/
5 soldiers dead today, in the Sinai.
More rarely also the western deserts are hit.
Excursions can be a risk, and even in the hotel you risk an attack.
If you want summer weather and bathing in the sea in the spring in a safe first-world-like environment, stay in the Americas. The closest place for European tourists looking for this is the gulf cooperation council countries but they're outrageously expensive and for bathing you have to stay in a resort so you as an american have much better options if the sea is your objective.