Agua pluvial or agua de lluvia – Rain water
Aguacero – a heavy rain storm
Arcoiris – rainbow
Baldazo – a lot of rain or bucketful of rain
Escampar – to clear up
Garua – a drizzle in Costa Rica
Garuar – verb to drizzle in Costa Rica
Cabeza de agua –  type of flash flood
Capa or impermeable – raincoat
Deslave – a wash out of a road
Estación lluviosa – rainy season
Inundación – a flood
Las desgracias no vienen solas – when it rains it pours
Llover a baldazos– to rain by the bucketful
Llover a cántaros – to pour or rain by the busketful
Llover a chorros – to rain copiously
Llover a cubetazos – also to rain by the bucketful
Llover perros y gatos – rain cats and dogs
Llover sobre mojado – to have one bad thing happen after another or when it rains it pours
Lloverle a uno – something bad or good is going to happen to you in abundance
Llovizna – drizzle
Lloviznar – to drizzle
Llueva o truene – come rain or shine
Lluvia de balas – a shower of bullets
Lluvia de piedras or flechas – raining stones or arrows
Lluvioso – rainy
Lluvia torrencial – torrential rain
No Llueve pero gotea – things are going to be OK but not as good as thy could be
onda tropical – a storm
Pelillo de gato – a mist in Costa Rica
Temporal – bad weather for a couple of days
Tromba – waterspout

Tiquismo of the week:
Después de la tormenta viene la calma – after the storm comes the calm
Después de la tormenta viene la cama – a vulgar version that means after a fight with your lover you reconcile in bed
Llover sapos y culebras – to rain toads and snakes