The climate of this district is characterised by its dryness and extremes of temperature and scanty rainfall. The year may be divided into four seasons. The cold season from November to March is followed by the Summer season which lasts upto the end of June. The period from July to about the middle of September and from the middle of September to October constitute the south west monsoon and post-monsoon seasons respectively.
Rainfall – Records of rainfall in the district are available for Sirsa only for sufficiently long periods. The average annual rainfall in the district is 32-53 mm. The rainfall in the district increases generally from west to east. About 72 percent of the annual normal rainfall in the district is received during the short south east monsoon period, July to September, July and August being the rainiest months. There is significant amount of rainfall in the month of June, mostly in the form of thunder showers. In the rest of the year, there is a very little rainfall. During the period 1901 to 1975, the highest annual rainfall as recorded was 327 percent of the normal in 1917. The lowest annual rainfall amounting to only 34 percent of the normal was recorded in 1920.
On an average there are 20 rainy days (i.e. days with rainfall of 2.5 mm or more) in a year in the district. The heaviest rainfall in 24 hours recorded in the district was 165.4 mm on September 22, 1917.
Temperature – There is no meteorological observatory in the district, so the mean meteorological conditions prevailing at GangaNagar and Hisar may be taken as representative of those prevailing in the district as general. There is a rapid increase of temperature after February. The mean daily maximum temperature during May and June which is the hottest period varies from 41.5 ºC to 46.7 ºC. On individual days the maximum temperature during the summer season may rise upto about 49 ºC. With the advance of the Monsoon into the district, by about the end of June, there is appreciably drop in the day temperature and the weather becomes cooler during the day time, but the nights are warmer than those during the summer season. With the added moisture in the monsoon air, the nights are often uncomfortable. The decrease in temperature is rapid after October and drop in temperature after nightfall is particularly trying. January is generally the coldest month with the mean daily maximum at 21.1 ºC and the mean daily minimum at 5.1 ºC.
Humidity – Relative humidity in the mornings is generally high during the monsoon season and during the period December to February, it is usually 70 percent or more. Humidity is comparatively less during the rest of the year, the driest part being the summer season with the relative humidity being about 30 percent in the afternoons.
Cloudiness – During the monsoon season, the sky is mostly moderately to heavily clouded. In the rest f the year, the sky is generally clear or lightly clouded. Cloudy sky prevails for brief spell of a day or two in association with passing western disturbances in the cold season.
Winds – Winds are generally light in the district with some strengthening in force during the late summer and monsoon seasons. During the south-west monsoon season while winds from south-west or west are more common, easterlies and south-easterlies also blow on some days. In the post monsoon and winter season while south-westerly or westerly winds are ore common in the mornings, northlies and north-westerlies are predominant in the afternoons. In summer, winds are more common from the west or south-west in the mornings. In the afternoons they are mostly from directions between west and north-west.
Special Weather Phenomena – Some of the depressions which originate in the Bay of Bengal in the south-west monsoon season, and which move across the central parts of the country reach the district during the last stages of activity and cause wide spread rain before dissipating. An occasional post-monsoon storm or depression also affects the district. Thunder Storms occur throughout the year but the highest incidence is during the monsoon season. Dust storms occur often during the hot season. Occasional fogs affect the district in the cold season.