Hi Sagarika -
Annika has given a very precise and accurate description of April.
If you are in the areas of lower altitudes, the fields will be plowed and, indeed, plants will be sprouting on the farms.
I have attached a panorama that I took in the Emmental (between Bern and Luzern )in mid April 2014. That year had an unusually dry and sunny April. I had only one rainy day and a couple of cloudy days during a 10 week trip. Most unusual. The weather in Spring is changeable and varies a lot over different regions of Switzerland. There are a lot of micro-climates which may differ from their neighbors 5 or 10 km away.
As you can see from the photo, the alps are still snow covered. However, the ski season is finishing, so many cable ways are not running
In the fields, the grass is still not fully green. In the sunny areas (Montreux, Weggis, The Cote Lavaux between Lausanne and Montreux), Spring always comes earlier because the sun is directly on those regions all day.
Taking walks or easy hikes is important for me in my visits to Switzerland. So, my attitudes are strongly infliuenced by the ability to find nice walks in Central Switzerland or the Emmental, free of snow. April is not always free of snow, but usually is OK for hiking in those regions. I really prefer to go in May. Spring has completely arrived in the lower elevations. I was lucky and surprised to have such good weather (as in the photograph) in April. If I want to go to the Engadine, especially the end near Austria ( Scuol, Ftan, Guarda) , where winter leaves a bit later, I prefer June... Wild flowers are everywhere; so are rain clouds, and the Summer services of the cable ways are mostly running by mid June.
In spite of the snow, you can see a lot in the Alps from the cograil train in any season. And, the villages are nice...particularly Wengen and Mürren.
Above all, remember that the weather in Switzerland, and the seasonal changes, are heavily influenced....controlled...by altitude. it is a lot colder longer into June in the Alps than it is at lower elevations such as Luzern and on the lakes. While the whole countryside is green and warm in early June near Bern or Geneva or Zürich, the highest Alpine pass highways may not yet be open until mid-June. Snow lingers.