It's almost the end of May and it can only mean one thing: It's haze season in Singapore again.

Last June, the PSI level in Singapore breached 401, signalling that the haze, courtesy of forest fires in Indonesia, was in the hazardous range.

This year, in anticipation of what could be a worse situation than last year -- which was already the worst haze episode in Singapore's history -- about 3.6 million free N95 face masks have been delivered to 1.2 million households nationwide from May 6 to 12.

These emergency preparedness starter kits are part of a distribution programme by Singapore Power, SingPost, and Temasek Cares, the philanthropic arm of Temasek Holdings.

The moment you find free N95 masks appearing at your front door overnight, you know something's up.

Here are 4 reasons why it has been predicted that the haze this year will surpass the 2013 asthma-inducing, lung-blackening levels:

1. Indonesian inaction

There is a lack of action in Jakarta due to an ongoing election that is distracting Indoensia from doing other things, such as ratify the Association of Southeast Asian Nations (ASEAN) 2002 Agreement on Transboundary Haze Pollution.

2. El Nino

A strong El Nino weather pattern can cause severe drought in Australia, Southeast Asia and India, while drenching other parts of the world such as the U.S. Midwest and Brazil in rain.

Singapore, as well as parts of Indonesia and Malaysia, could experience intense haze for a few months as dry conditions kick in.

3. No one knows who is responsible for fires

There is simply no easy way to find out who is responsible for the haze given the lack of evidence like maps showing who owns the land where fires are burning. Both Indonesia and Malaysia have refused to share clear and updated maps about land use so far.

4. Parts of Indonesia are already burning

In February, Indonesia's Riau province had already declared a state of emergency as fires there are reportedly worse than last year's. Haze from raging forest fires caused tens of thousands to fall sick with respiratory problems and shut down the airport in the provincial capital for more than three weeks.

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