Yemen's civilians are facing an "immeasurable" crisis with the onset of the Muslim holy month of Ramadan, according to the UN.

A ceasefire has improved humanitarian access, but some areas are still very hard to reach.

On Yemen's Red Sea coast, temperatures often exceed 40C and erratic electricity supplies make observing the fast - where Muslims refrain from eating or drinking from dawn to dusk - particularly challenging.

"We're suffering not only poverty, but frequent power cuts and lack of water," Abdu Abdullah Gharefah, a Hudeida resident, told Al Jazeera.

"This is causing disease to spread among adults and children. Our life is difficult but we're holding on."

The Yemen conflict has killed more than 6,400 people and displaced 2.8 million since March last year.

Almost 14 million Yemenis need humanitarian assistance.

The UN says food, fuel and medicines are in short supply and that has pushed prices up.

"This could be the worst year in the history of Yemen, especially with the start of the holy month of Ramadan," Abdesalam al-Mahtoury, an economic analyst, said.

"No doubt prices have gone up as a result of the siege that's been imposed for more than 14 months."

The UN says imports are still restricted and many cargo ships cannot offload at Yemen's ports. It is appealing for $1.8bn in aid for Yemen this year.

So far, it says, it has received just 17 percent of that.