Air pollution in Singapore reached its highest level this year on Wednesday, as smoke from wildfires in Indonesia drifted over the city.

The hourly reading of fine particles, known as PM2.5, hit 284 in western Singapore at 2 p.m. local time, Reuters reported. That put it in the "very high" band for the first time in the current haze. By 3 p.m., the reading in the west had risen to 288, CNA reported. Readings in other parts of the island were in the high or elevated range.

The smoke is coming from fires in Kalimantan and southern Sumatra, Singapore's environment agency said, CNA reported. Indonesia is facing its worst wildfire season in 11 years, driven by dry El Niño weather, Reuters reported.

When readings are very high, people should cut back on outdoor activity, CNA said. Older people, pregnant women and children should avoid going outside altogether. Sport Singapore closed outdoor sports centers in the west, and a SAFRA clubhouse in Toa Payoh shut its swimming pool, The Straits Times reported.

The government has said it will hand out N95 masks to vulnerable people if air quality gets worse, CNA reported. Schools may also close if the 24-hour air index is forecast to reach the "hazardous" range.

Reuters reported that the haze has also hurt air quality across the region. East Timor said it will stop in-person classes for three days starting on Thursday, Reuters reported. Several states in Malaysia have also closed schools, it said.

Officials expect dry weather to continue in fire-prone areas, so the risk of severe haze remains, CNA reported.

What we know: Air pollution in western Singapore reached the very high range on Wednesday because of smoke from Indonesia.
What we don't: How long the haze will last, or whether schools in Singapore will need to close.