Day temperature above ‘normal value,’ nights turn colder

With day temperatures apparently on an upward spiral and night temperatures falling below normal values, the capital city is in the grip of a hot spell.

On Thursday, Thiruvananthapuram recorded a maximum temperature of 34 degree Celsius and minimum of 22 C. According to K. Santhosh, director of the Met Centre here, the maximum temperature on the day is higher than the ‘long period average temperature’ for the capital city. This reading, also called the normal value, is the average maximum temperature recorded in the city for the past 40 years. For Thiruvananthapuram, this value for the month of March is 33.2 C. On March 9, 10 and 12, the maximum temperature in the city was one degree above the normal value.

“The current hot spell is caused by a high pressure area dominating the southern peninsula. This hampers cloud development. Low humidity levels coupled with a cloud-free atmosphere leads to a rise in the temperature. This hot spell is expected to continue till March 19 when isolated thundershowers are expected in the southern districts of the State. The equinox falls on March 21. Till mid-April this region would get greater and stronger sunshine,” Mr. Santhosh told The Hindu on Friday.

However, the stronger sunshine is also expected to trigger what meteorologists call “moisture incursion” from both the Arabian sea and the Bay of Bengal. Moreover, a “trough” is also expected to form over the peninsular region leading to rainfall by around April 14.

The current hot spell also means that the “diurnal variation” or the difference between the highest temperature and the lowest temperature on any day is also high. For Thiruvananthapuram the normal value in March for the minimum temperature is 24 C. On Wednesday, the minimum temperature in the city was 22 C.

Mr. Santhosh, however, added that the city’s daily maximum temperature—high as it is—is not high enough to cause sunstroke. “This temperature may cause sunburns, but sunstroke is caused only in those areas where the long period average temperature is above 40 degrees. In no place in Kerala is this value above 40.”

On Wednesday, Kottayam recorded a maximum temperature of 38 C. This is but half a degree less than the all-time high maximum temperature of 38.5 degrees recorded in the district on March 9, 2004.