Climate
According to the established classification for Bulgaria, the territory of Rila National Park falls entirely within the mountain climatic zone of altitudes of 1,000 m. and over. Otherwise, the Park lies at the boundary between the moderate-continental and the transitional-Mediterranean climatic zones.

The lowest temperatures for Rila mountain have been recorded at its highest peak, Mussala (2,925 m. a.s.l.): an all time low of –31.2°C; the coldest month is February, with an average monthly temperature of –11.6°C; the all-time high for Mussala Peak is +18.7°C.

On the whole, sub-zero mean daily temperatures may last for up to 9 months of the year, often till the end of June. A steady rise in temperatures is observed towards the end of July, but even in high summer the mean daily temperature hardly ever climbs above the 10°C mark. On between 5 and 10 days each in June, July and August, the mean daily temperatures may rise to above 15°C. This determines the relatively short vegetation cycle within the Park, which varies in duration between 3 and 6 months, lasting for about 3 months at altitudes higher than 2,000 m. a.s.l.

Solar radiation is the key factor determining temperature conditions within the Park. In the lower reaches of the mountain, where clouds are scarcer, the annual amount of sunshine is an average of 2,176 hours. As more and thicker clouds gather above the mountain slopes with the increase in altitude, solar radiation diminishes to around 1,900 hours on Mussala Peak. The monthly duration of sunshine in Rila National Park is shortest in December, and longest in August, 248 hours.

In the higher portions of Rila National Park, relative air humidity it typically between 80 and 85%. The cold winter months are usually the driest. Also, humidity differs with exposure, between the northern and southern slopes of the mountain.

Precipitation also varies with exposure. In winter, snowfall on the southern mountain slopes may reach 22-25% of the annual norm, while on the northern slopes winter precipitation is scarcer. On the western and northern slopes, precipitation reaches its annual peak in the summer season, while on the eastern slopes this happens in winter.

A lasting snow cover forms in the lower zones of Rila National Park after December 10-15 for the northern slopes, and after December 20-30 for the southern slopes. The snow cover holds for 200-220 days of the year, and at lower altitudes is usually thickest in February, with a monthly average of 20-30 cm. Conversely, at higher altitudes of 2,000 m. a.s.l. or over, the snow cover in thickest in March: 70-80 cm, while in the highest portions of the Park territory the snow may pile up to 200-240 cm. in thickness. The average annual duration of the period of steady snow cover is 70-80 days for altitudes under 1,200-1,300 m., but may reach 180-200 days for altitudes of 2,000 m. or over.

The prevailing winds in the territory of Rila National Park are westerly southwesterly, coming in with speeds of up to 30-40 m./sec. (over 100 km./h) Northwesterly and easterly winds are somewhat more moderate. The average monthly wind speed at the highest mountain peaks may reach 11-12 m. /sec., while inn the lowest mountain reaches the average wind speed varies between 1.2 -2.5 m. /sec., and at middle altitudes, between 2.5-3.2 m. /sec.

Waters
Rila National Park occupies a scant 0.73% of the territory of Bulgaria, yet accounts for about 3.61% of the country’s water resources, as much as 9.40% of the combined outflow of the rivers Struma and Mesta; 5.62% of the river Maritsa, and 8.27% of the Iskar. The Park is situated amid one of the areas in Bulgaria that are richest in surface water basins. The combined outflow of all rivers and water streams in the territory of Rila National Park is 700.4m cu.m. per annum. The combined volume of all lakes within the Park is 80m cu.m.

For the higher portions of Rila National Park, the average annual amount of precipitation is in the order of 1,050-1,200 mm./sq.m, while in the lower park territories it is considerably lower, 700-800 mm./sq.m. Spring thaw at higher altitudes begins in mid-April and sometimes is not completed until June. The steady snow cover formed within the boundaries of Rila National Park is the principal source of clean drinking water for the surrounding communities and the city of Sofia.

A considerable number of hydrotechnical facilities and installations operate in the territory of Rila National Park for the purpose of deflecting and redistributing the natural water outflow according to needs.

Soils
The territory of Rila National Park falls within middle and high-altitude belt of the Thracian forest vegetation zone, sub-zone Rila.

The middle forest vegetation belt starts at altitudes of 700 m. and ends at 2,000-m. a.s.l. The principal soils in this zone are brown forest (at 700-1,200 m.), and forest-mountainous dark soils (1,200-2,000 m.).

The high-mountain forest vegetation zone comprises the highest portions of Rila Mountain, at altitudes between 2,000 and 2,500 meters. The principal types of soil there are two: forest-mountainous dark soils and meadow-mountainous soils. The former are common for both the middle and high altitudes, occupying the dwarf-pine and sub-alpine pasture zone, while the latter are exclusively characteristic of the alpine pastures.

Thus it can be said that the territory of Rila National Park is dominated by brown forest, forest-mountainous dark and meadow-mountainous soils with a humus layer of medium thickness.