Learn Russian: Благодаря хорошей погоде гости съезжаются на фестиваль. - Thanks to the good weather, guests are gathering for the festival.

The prefix с- here means convergence or coming together from different places. When added to a verb of motion like ездить (to go by transport) along with the reflexive suffix -ся (indicating a mutual action), it literally means "driving together to one place". If the guests were walking, you would use сходятся instead.

Why is there a hard sign (ъ) in съезжаются?

The hard sign ъ acts as a separator. It is required when a prefix ends in a consonant (like с-) and the root starts with a soft vowel like е, ё, ю, or я. It stops the consonant from blending into the vowel, ensuring the с stays hard and the е keeps its distinct "ye" sound.

Why is хорошей погоде in the Dative case?

The preposition благодаря (thanks to) always requires the Dative case. Even though the related verb благодарить (to thank) takes the Accusative case for the person you are thanking, this preposition itself forces the noun phrase that follows into the Dative.

Why is it на фестиваль (Accusative) rather than the Prepositional case?