New Delhi, Nov 25 : Delhi-NCR's air quality which will deteriorate to the 'very poor' category for two days starting Thursday will register a slight improvement from November 27, Air Quality Early Warning System for Delhi (Ministry of Earth Sciences) said in its bulletin. The air quality is likely to remain in 'very poor' category. Gradual improvement is likely from November 27. PM2.5 to be the predominant pollutant, it said. "Local surface winds are relatively low for the next three days that reduces dispersion of pollutants leading to deterioration of air quality but air quality is likely to be in higher end of 'very poor' category for the next two days. On November 27, local surface winds are likely to increase resulting in improvement of air quality but expected to be within avery poor' category. The effective fire count is 432 and its share in Delhi's PM 2.5 is 2 per cent. With the onset of winter conditions local weather is likely to be dominating in determining air quality," System of Air Quality and Weather Forecasting And Research (SAFAR) stated. The level of PM 2.5 and PM 10 are under satisfactory and moderate category with overall air quality of 339 on Thursday. An AQI between zero and 50 is considered 'good', 51 and 100 'satisfactory', 101 and 200 'moderate', 201 and 300 'poor', 301 and 400 'very poor', then 401 and between 500 is considered 'severe'. Meanwhile, Delhi woke up to a mainly clear sky with its maximum temperature being pegged at 28 degrees Celsius and minimum at 10 degrees. The relative humidity at 8.30 a.m. was recorded at 95 per cent. According to India Meteorological Department, the national capital will witness foggy mornings this entire week. /IANS