The monsoon season in Dhaka lasts from June to September, during which time the city experiences heavy rainfall and occasional flooding. This season can also bring some relief from the extreme heat.

In terms of extreme temperature, the hottest months of the year in Dhaka are generally April, May, and June, with temperatures often exceeding 35 degrees Celsius (95 degrees Fahrenheit). The coldest months are typically December and January, with temperatures ranging from 10 to 20 degrees Celsius (50 to 68 degrees Fahrenheit).

However, due to climate change, extreme weather events are becoming more frequent and unpredictable. So, it is essential to keep an eye on weather forecasts and take necessary precautions to stay safe during extreme temperature events.

1. Summer: The summer season in Dhaka lasts from March to June. During this time, the temperature can rise to as high as 40 degrees Celsius (104 degrees Fahrenheit), with high humidity levels making it feel even hotter. This season is characterized by clear skies and occasional thunderstorms. It is essential to stay hydrated and avoid outdoor activities during the hottest hours of the day to avoid heat-related illnesses.
2. Monsoon: The monsoon season in Dhaka lasts from June to September. During this time, the city experiences heavy rainfall, often leading to flooding in low-lying areas. The temperature during this season ranges from 25 to 32 degrees Celsius (77 to 90 degrees Fahrenheit), with high humidity levels. It is essential to take necessary precautions during the monsoon season, such as avoiding flood-prone areas and carrying umbrellas or raincoats.
3. Winter: The winter season in Dhaka lasts from November to February. During this time, the temperature drops to as low as 10 degrees Celsius (50 degrees Fahrenheit), with occasional foggy mornings. It is generally a pleasant season, with clear skies and low humidity levels. However, it is essential to keep warm during the colder months, especially during the nighttime.

Here are some possible causes of heat waves in Dhaka city:

1. Urbanization: Rapid urbanization and the growth of the city’s population have led to increased heat absorption and reduced ventilation, resulting in higher temperatures in urban areas. The urban heat island effect, which is the phenomenon of cities being significantly warmer than surrounding rural areas, can exacerbate the effects of a heat wave.
2. Climate change: The global rise in temperatures due to climate change has led to an increase in the frequency and intensity of heat waves worldwide, including in Dhaka city. Climate change can cause extreme weather events, such as heat waves, droughts, and floods, which can have severe consequences for human health and the environment.
3. Deforestation: The loss of trees and green spaces in Dhaka city has contributed to the urban heat island effect and reduced the city’s ability to regulate temperature and humidity levels. Trees and vegetation act as natural air conditioners by absorbing heat and releasing water vapor through a process called transpiration.
4. Air pollution: High levels of air pollution in Dhaka city can worsen the effects of a heat wave by trapping heat and reducing air quality, leading to respiratory problems and other health issues. Air pollution is caused by various sources, including transportation, industries, and open burning.
5. Weather patterns: Natural weather patterns, such as El Nino, can contribute to the occurrence of heat waves in Dhaka city. El Nino is a climate pattern that occurs every few years, leading to warmer ocean temperatures and changes in global weather patterns.

A heat wave is a prolonged period of unusually hot weather, which is typically characterized by high temperatures and high humidity levels. Heat waves can occur in both humid and dry climates and can last from a few days to several weeks.

During a heat wave, the temperature remains consistently high, often exceeding the average maximum temperature for a particular location and time of year. The heat wave can cause a variety of health problems, particularly in vulnerable populations, such as children, the elderly, and people with pre-existing medical conditions.

The human body relies on the regulation of internal temperature to function correctly, and prolonged exposure to high temperatures can lead to dehydration, heat exhaustion, heat cramps, and in severe cases, heat stroke, which can be life-threatening. Other adverse effects of heat waves include increased air pollution, power outages due to high demand for air conditioning, and damage to crops and infrastructure.

Heat waves can be caused by a variety of factors, including climate change, changes in weather patterns, and urbanization. It is essential to take necessary precautions during a heat wave, such as staying hydrated, avoiding outdoor activities during the hottest hours of the day, and seeking shelter in air-conditioned or shaded areas.

There are two main types of heat waves: dry heat waves and humid heat waves.

1. Dry Heat Waves: Dry heat waves occur in areas with low humidity levels and typically have high daytime temperatures and low nighttime temperatures. These heat waves are often associated with clear skies and can cause dehydration and heat exhaustion, especially in areas with high solar radiation.
2. Humid Heat Waves: Humid heat waves occur in areas with high humidity levels and are often characterized by high daytime temperatures and high nighttime temperatures. These heat waves are usually associated with cloudy skies and can cause more significant health impacts due to the higher levels of atmospheric moisture. The high humidity levels can make it difficult for the body to cool itself through sweating, leading to an increased risk of heat stroke and other heat-related illnesses.

In addition to these two main types, heat waves can also be categorized based on their duration, intensity, and timing. Some other types of heat waves include:

1. Flash heat waves: These heat waves occur suddenly and without warning, typically lasting for a few hours to a day.
2. Summer heat waves: These heat waves are often the most prolonged and intense, occurring during the summer months and lasting for several days to weeks.
3. Tropical heat waves: These heat waves occur in tropical regions and are often associated with high humidity levels and frequent thunderstorms.
4. Urban heat waves: These heat waves occur in urban areas and are often exacerbated by the urban heat island effect, which causes cities to be significantly warmer than surrounding rural areas.

The measurement of heat waves involves analyzing a combination of temperature, humidity, and duration of the high temperatures. The following are some of the commonly used measures to determine heat waves:

1. Maximum temperature: This is the highest temperature recorded during a heat wave. In some cases, a heat wave is defined as a period of several consecutive days during which the maximum temperature exceeds a certain threshold, such as 32°C (90°F) or 35°C (95°F).
2. Heat index: This is a measure of how hot it feels to the body when relative humidity is taken into account along with the air temperature. The heat index combines temperature and humidity to produce a “feels-like” temperature, which can be a more accurate measure of the level of discomfort caused by heat.
3. Wet bulb globe temperature (WBGT): This is a measure of heat stress in humans that takes into account the effects of temperature, humidity, wind speed, and solar radiation. It is commonly used to assess the risk of heat exhaustion and heat stroke in outdoor workers, athletes, and military personnel.
4. Cooling degree days (CDD): This is a measure of the amount of cooling needed to maintain indoor temperature at a comfortable level during a heat wave. It is calculated by subtracting the average daily temperature from a reference temperature (usually 65°F or 18°C) and summing the results over a specified period.

Heat waves are natural phenomena that cannot be controlled, but we can take steps to reduce their impact on our health and the environment. Here are some ways to mitigate the effects of heat waves:

1. Stay hydrated: During a heat wave, it is crucial to stay hydrated by drinking plenty of fluids, especially water. Avoid alcohol and caffeine, which can dehydrate the body.
2. Keep cool: Stay in air-conditioned or well-ventilated areas as much as possible during a heat wave. Use fans or air conditioning to keep the air circulating and reduce indoor temperatures.
3. Dress appropriately: Wear light-colored, loose-fitting clothing made from breathable fabrics, such as cotton or linen, to help keep cool.
4. Avoid outdoor activities: During the hottest hours of the day, avoid strenuous outdoor activities, such as exercise or gardening.
5. Check on vulnerable individuals: Check on elderly or sick relatives, friends, or neighbors to ensure they are coping with the heat. Infants and young children are also at increased risk during heat waves.
6. Reduce energy use: Avoid using energy-intensive appliances during the hottest hours of the day to reduce strain on the power grid. This will also help lower your energy bills and reduce greenhouse gas emissions.
7. Green infrastructure: Implementing green infrastructure, such as planting trees or green roofs, can help reduce urban heat island effects and provide shade.
8. Climate action: Taking steps to reduce greenhouse gas emissions, such as using renewable energy sources and reducing carbon emissions from transportation, can help mitigate the long-term impacts of climate change and reduce the frequency and severity of heat waves.

During a heat wave, it is important to take necessary precautions to protect yourself from heat-related illnesses. Here are some things you can do during a heat wave:

1. Stay hydrated: Drink plenty of fluids, especially water, to prevent dehydration. Avoid alcohol and caffeine, which can dehydrate the body.
2. Keep cool: Stay in air-conditioned or well-ventilated areas as much as possible during a heat wave. Use fans or air conditioning to keep the air circulating and reduce indoor temperatures. If you don’t have access to air conditioning, try to find public places with air conditioning, such as libraries or shopping malls.
3. Dress appropriately: Wear light-colored, loose-fitting clothing made from breathable fabrics, such as cotton or linen, to help keep cool.
4. Avoid outdoor activities: During the hottest hours of the day, avoid strenuous outdoor activities, such as exercise or gardening. If you must be outdoors, take frequent breaks in shaded or air-conditioned areas.
5. Check on vulnerable individuals: Check on elderly or sick relatives, friends, or neighbors to ensure they are coping with the heat. Infants and young children are also at increased risk during heat waves.
6. Eat light: Eat light, cool, and easy-to-digest foods, such as fruits and vegetables, to help regulate your body temperature.
7. Use sunscreen: Apply sunscreen with a high SPF to protect your skin from the harmful effects of the sun.
8. Seek medical attention if necessary: If you experience symptoms such as dizziness, nausea, headache, or confusion, seek medical attention immediately as these could be signs of heat exhaustion or heat stroke.

Heat waves can pose significant health risks, particularly for vulnerable populations, such as the elderly, young children, pregnant women, and people with pre-existing medical conditions. Here are some possible health risks due to heat waves:

1. Dehydration: Heat waves can cause dehydration, which can lead to fatigue, weakness, dizziness, and in severe cases, heat exhaustion or heat stroke.
2. Heat exhaustion: Prolonged exposure to high temperatures can lead to heat exhaustion, which is characterized by symptoms such as heavy sweating, nausea, headache, dizziness, and fainting.
3. Heat stroke: Heat stroke is a medical emergency that can occur when the body’s temperature regulation system fails, and the body temperature rises to dangerous levels. Symptoms of heat stroke include confusion, seizures, rapid heartbeat, and loss of consciousness.
4. Respiratory problems: Heat waves can worsen respiratory problems, such as asthma and chronic obstructive pulmonary disease (COPD), as high temperatures can increase air pollution and trigger breathing difficulties.
5. Cardiovascular problems: Heat waves can put a strain on the cardiovascular system, leading to increased heart rate, blood pressure, and the risk of heart attack and stroke.
6. Mental health: Prolonged exposure to high temperatures can also affect mental health, causing irritability, anxiety, and even depression.

The coldest month in Dhaka, the capital city of Bangladesh, is typically January, with an average temperature of around 19-20°C (66-68°F). However, it is important to note that the temperature can still feel quite warm and humid, as Dhaka is located in a tropical region with high levels of humidity throughout the year.

The hottest month in Bangladesh is usually April, with temperatures ranging from 26-34°C (79-93°F) across the country. This is the peak of the summer season in Bangladesh and is characterized by high levels of humidity, making it feel even hotter.

Overall, Dhaka can be considered a hot city, with average temperatures ranging from 24-34°C (75-93°F) throughout the year. However, the city also experiences significant rainfall during the monsoon season, which runs from June to September, providing some relief from the heat.

The hottest city in Bangladesh is generally considered to be Rajshahi, located in the northwest region of the country. This city has a semi-arid climate and can experience temperatures as high as 45°C (113°F) during the summer months. Other cities in Bangladesh, such as Chittagong and Sylhet, also experience hot and humid weather throughout the year.

Preparing for a heat wave in the future is important to protect yourself and your community from the harmful effects of extreme heat. Here are some steps you can take to prepare for a heat wave:

1. Stay informed: Keep track of weather forecasts and heat warnings issued by local authorities. Sign up for emergency alerts to receive notifications about heat waves and other weather-related emergencies.
2. Plan ahead: If you have to go outside during a heat wave, plan your activities for the early morning or late evening when temperatures are cooler. Avoid strenuous activities during the hottest hours of the day.
3. Stay cool: Invest in air conditioning or fans to keep your home cool during a heat wave. If you do not have access to air conditioning, consider visiting public places with air conditioning, such as libraries or shopping malls.
4. Stay hydrated: Drink plenty of fluids, especially water, to stay hydrated and prevent dehydration. Avoid alcohol and caffeine, which can dehydrate the body.
5. Dress appropriately: Wear loose-fitting, light-colored clothing made from breathable fabrics to stay cool during a heat wave.
6. Protect vulnerable populations: Check on elderly or sick relatives, friends, or neighbors to ensure they are coping with the heat. Infants and young children are also at increased risk during heat waves.
7. Prepare an emergency kit: Prepare an emergency kit with essential items such as water, non-perishable food, and first aid supplies in case of a power outage or other emergencies during a heat wave.
8. Reduce energy use: Reduce energy use during a heat wave to prevent power outages and reduce strain on the power grid. This includes turning off unnecessary lights and appliances and avoiding using the oven or stove during the hottest hours of the day.

1. Shade: Trees provide shade, which can help reduce the temperature in urban areas. In cities, tree cover can also reduce the temperature of buildings and streets, which can help mitigate the “urban heat island” effect.
2. Evapotranspiration: Trees absorb water from the soil and release it into the air through a process called evapotranspiration. This process cools the surrounding air and increases humidity levels, which can help make the environment more comfortable during a heat wave.
3. Air quality: Trees can help improve air quality by absorbing pollutants and releasing oxygen. During a heat wave, air quality can be especially poor due to increased levels of pollutants, so having more trees can help improve the overall air quality and reduce the health risks associated with heat waves.
4. Ecosystem services: Trees provide a range of ecosystem services that can help reduce the effects of heat waves, such as carbon sequestration, soil conservation, and biodiversity conservation.

Overall, tree plantations can play an important role in mitigating the effects of heat waves by providing shade, reducing the amount of heat absorbed by the ground, and increasing the amount of moisture in the air. Planting trees in urban areas, along streets and in public spaces, and in residential areas can all help to create a more comfortable and resilient environment during a heat wave.