rainy weather is not helpful to a young bee hive, short on resources. like puppies, you have to keep the food constant and plentiful.
a 1/2 gallon container of 1:1 sugar/water mix helps keep the bees happy and keeps them focused on drawing out the wax frames. the hive will run thru 1/2 gallon of water about every three days, depending upon weather - the better the weather, the more bees fly and they do prefer real nectar and will eventually wean themselves from the sugar water when nectar is plentiful.
until then, costco and 20 pound sacks of sugar for the foreseeable future.