Second Ever April Heatwave for Antigua

Dale C. S. Destin |

We can now confirm that we are in a heatwave, which started a week ago.

For us, a heatwave is declared when there has been at least six consecutive days of high temperature in the top 10% of the climatological normal period 1971-2000, or is well above what is considered normal.

Since last Friday, the average high temperature has been well above normal – 31.4 °C (88.5 F). This is 1.8 °C (3.2 °F) above the average for the same period. The high temperature, on average, has been higher than that of August – 31.2 °C (88.2 °F), the month with the top mean high temperature.

The excess temperature of 1.8 °C (3.2 °F) may not seem like a lot but it is in fact quite significant. Think about it: The average body temperature is 37 °C (98.6 °F). A temperature exceeding 37.6 °C (99.7 °F) is considered a fever.  If your body temperature were to rise by 1.8 °C, you would need immediate medical attention.

Notwithstanding the actual temperatures measured, the heat index or the “feel like” temperatures have been running much higher. The “feel like” temperature is a measure of how hot it really feels to the body when the actual temperature is adjusted to take into account the humidity.

The average relative humidity for Antigua during the warmest part of the day has been around 58 percent. This translates to “feel like” temperatures in the range of 34-36 °C (93-97 °F). Extreme caution is required to prevent heat related illness from such high values of “feel like” temperatures.

Even more alarming, according to the US National Weather Service, exposure to full sunshine can dramatically increase the “feel like” temperature by up to 8.3 °C (15 °F). Thus, for persons in built-up areas of Antigua such as St. John’s City, the “feel like” temperature may have been “hell like”.

Based on the data at the Airport, the last heatwave was in March/April 2010. It lasted for 11 days. However, there has only been one other heatwave in April proper – April 5-13, 1998. Back then the average high was also 31.4 °C. However, the relative humidity was much higher – around 70%; hence, the “feel like” temperature was also much higher – 39 °C (102 °F), on average.

What should be done to avoid the potential harm of a heatwave? Residents are urged to take it easy during strenuous activities from around midmorning to midafternoon, as well as drink plenty of water. That is especially true for the elderly, children and those sensitive to the heat.

Protection against ultraviolet (UV) radiation to prevent sunburn is also highly recommended. The UV index is generally high all-year-round in our area; however, with the low cloud coverage expected for the rest of the week, the index will be off the chart.

The heatwave is expected to come to an end by Sunday; however, warmer than normal high temperatures are possible for some days next week. In the long run, near to above average temperatures are expected to prevail for the upcoming three months.