for the sencence "Yesterday the weather WAS good at the beach"
if you want to use the verb 'TO BE' in spanish you can say
Ayer en la playa el tiempo ERA bueno.
otherwise you can say
Ayer hizo buen tiempo en la playa
which is NOT a DIRECT translation from english, but it is a trasnlation that is way more common than the previous one
Hope it helps :)
Saludos