Daily PM2.5 Heatmap for Peninsular Malaysia July - October 2025

Introduction

This interactive dashboard provides a view of the 2025 July to October haze period. On the Left, the Voronoi-based spatial interpolation shows how smoke and particulate matter move across the Peninsula. On the Right, the time-series plot tracks the intensity spikes.

By using the navigation bar at the top of the graphics, you can scrub through specific dates to observe the correlation between regional averages (black line) and local station variances (faint lines).

Observations & Haze Analysis

The July Spike: According to reports from The Star and Bernama on July 20, 2025, air quality plummeted to unhealthy levels in several key areas. Nilai recorded the highest API at 162, followed closely by Banting and Johan Setia at 154. Department of Environment (DOE) officials confirmed that this deterioration was primarily due to transboundary haze drifting across the Straits of Malacca, as no large-scale local fires were detected in Malaysia at the time.

Source of the Fires: Satellite imagery from the ASEAN Specialised Meteorological Centre (ASMC) identified the root cause as a massive surge in hotspots across Sumatra, Indonesia. Over 1,200 hotspots were detected in Sumatra alone during this period, with Riau province being the most severely affected. Prevailing southwesterly monsoon winds carried the resulting smoke plumes directly toward the west coast of Peninsular Malaysia, specifically impacting Selangor, Negeri Sembilan, and Melaka.

The September Spike: The secondary spike visible in the data between September 18 and September 27 corresponds with the tail-end of the Southwest Monsoon. This period may present a second wave of dry weather in the southern ASEAN region. During these weeks, persistent peatland fires and agricultural biomass burning in Central Sumatra and West Kalimantan intensified. This created a sustained corridor of transboundary smoke that traveled across the peninsula before the inter-monsoon rains finally arrived in October to clear the skies.

Regional Context: These events underscore the seasonal vulnerability of Peninsular Malaysia. While the bold black line in the graph shows the regional average, the individual gray lines reveal how stations in Kuala Lumpur, Selangor (e.g. Johan Setia) often bear a disproportionate burden, frequently spiking well above the average due to their geographical position along the primary wind path of the haze from Sumatra.