16 August,2026 07:36 AM IST | Mumbai | Eeshanpriya MS
IMD head scientist Bikram Singh tells about what to expect this monsoon. Pic/Atul Kamble
In light of the India Meteorological Department's (IMD) warning of below normal rainfall this monsoon season under the effect of El-Nino, Regional Meteorological Centre's (IMD Mumbai) head scientist Bikram Singh spoke to Sunday mid-day about rainfall patterns noticed in Mumbai and Maharashtra in July, the weak monsoon start to the month of August, and how the effect of El-Nino is likely to affect the latter half of the monsoon season - mid August to September; he also talked about IMD's impact based forecast, and reasons why IMD gives its red and orange alerts.
While 65 per cent of the decision is driven by the quantum of rainfall, alerts are issued for administrative preparedness. Singh said, "A lot of thought goes into sounding a red or yellow or orange warning."
Speaking about what the alerts mean, Singh indicated that they are meant to not just alert citizens, but also alert authorities on "associated impact" - a red alert can be issued on a day that follows several high rainfall days. Singh said these alerts also account for wind speed, landslide, waterlogging, thunderstorms, or flash floods.
On what basis does IMD give alerts?
While 65 per cent of the decision is driven by the quantum of rainfall, alerts are issued for administrative preparedness. A lot of thought goes into sounding a red or yellow or orange warning because we are answerable to authorities that take response and preparedness decisions based on our warnings.
We also give impact based alerts by gauging situations which can have an âassociated impact', in addition to the quantum of rainfall as per our predictions.
For instance, if IMD issued a red alert for five consecutive days, on the sixth day, we would have already noticed that the rainfall activity is going to reduce. However, we will still issue a red alert (despite the expectation of low quantum of rainfall), to ensure everyone is prepared to handle the aftermath of a past heavy spell even during a light spell day; because the impact persists even if the rain subsides.
We are also exceptionally careful about the red alerts in the ghats section. If you will notice, we give red alerts more leniently during the month of August, because due to June and July's rainfall, the soil is already saturated. The possibility of a landslide becomes highest in August and September, so we immediately issue a red alert.
Regarding amount of rainfall expected, IMD has a clear formula
Very Light: 0.1 to 2.4 mm
Light: 2.5-15.5 mm
Moderate: 15.6-64.4 mm
Heavy: 64.5-115.5 mm
Very Heavy: 115.6-204.4 mm
Extremely Heavy: ⥠204.5 mm
Exceptionally Heavy:
When the amount is a value near about the highest recorded rainfall at or near the station for the month or season. However, this term will be used only when the actual rainfall amount exceeds 12 cm
What do the alerts mean?
>Red alert means there is a warning and a need to take action.
>Orange alert means there is a need to be prepared to take action
>Yellow alert means there is a need to be watchful and aware
> Green alert means no action is required.
>Ideally, a green alert indicates light to moderate rainfall, as is expected during the monsoon season.
>A yellow alert is meant to tell citizens to be aware of rain, carry an umbrella, plan a commute, etc.
>An orange alert informs citizens that they can stay at home if possible, be vigilant, watch news and communication from local authorities. Authorities are alerted to watch low-lying areas, issue warnings for those living on river banks, assign dewatering pumps, etc.
> A red alert indicates extremely heavy rainfall. It also helps local authorities decide if schools need to be given a holiday, and how the emergency situation needs to be monitored from that point forward to prevent mishaps or untoward incidents.
Can you cite any examples?
For example: Mumbai had a red alert on July 4 and 5, 2026. Immediately before that, it was an orange alert. So the red alert was also issued considering that under an orange alert the city has already received a lot of rain, our systems are already operating at full response capacity - you can say on fire fighting mode.
Given this, a consecutive spell of rain qualifies for a red alert, because we have to consider the fact that the soil has already saturated with its water absorption capacity.
Example: Similarly, two years ago, Matheran had two days of intense rain, and a red alert was issued considering the amount of rainfall that was expected/anticipated. However, on the third day, despite low rainfall we continued the red alert. Because Matheran has lost red soil. It had already reached its saturation capacity. Even little subsequent rainfall can now lead to a landslide.
For this single purpose, we have also started to give additional information or warnings at the bottom of all our daily forecast, that predict the associated impact or an orange or a red alert, such as:
Impact Expected:
>Localised inundation/flooding of low-lying areas and urban areas.
>Possible uprooting of weak trees and collapse of old and unmaintained structures.
>Possibility of flash floods.
> Disruption to road, rail, air and ferry transport.
> Local disruption of municipal services (Water, electricity etc.).
> Flow of water over low-lying roads and bridges.
> Damage to horticulture and standing crops due to water inundation.
> Squally weather expected over coastal districts of Konkan.
> Rough sea conditions along the coast.
> It may lead to riverine flooding in some river catchments (for riverine flooding please visit the Central Water Commission webpage).
> Landslide/Mudslides and rock falls in vulnerable areas.
> Strong wind may damage plantations, horticulture and standing crops.
> Minor damage to kutcha houses/walls and huts.
> Possibility of cloud to ground lightning during thunderstorm events.
August so far did not receive much rainfall in comparison to July. Is it expected that August will receive weak rainfall?
So far, the condition is . We have managed to match the seasonal rainfall expectation due to July's rainfall. If we examine the entire season's rainfall, Mumbai is not in deficit. There are some districts of Maharashtra that indicate a deficit in annual average rainfall, but overall, the state has received good rainfall this season so far. El Nino factor is likely to intensify during the later part of the monsoon season, towards the end of August and in September. We can expect weak rainfall during this period due to El Nino. We should be prepared for less rainfall going forward for the remainder of the monsoon season.
At present, 10 districts of Maharashtra have deficient rainfall: Nandurbar, Amravati, Nagpur, Akola, Chandrapur, Jalna, Hingoli, Beed, Solapur, and Sindhudurg. Only Nashik has a large excess rainfall, and Chhatrapati Sambhaji Nagar, Pune, Palghar, and Mumbai suburbs have excess rainfall.
IMD had predicted a weak monsoon (below normal monsoon) owing to El-Nino. How has this affected the monsoon season?
The lack of sustained rainfall, short periods of heavy rainfall or sudden intense rain spell, followed by a considerable dry spell, are all signatures of El-Nino.
We have already noticed this during the intense rainfall spell of the first week of July, followed by a considerable dry spell. The whole of Maharashtra did not have any rainfall during June.
We must consider temporal variation - if we examine the week to week rainfall pattern - the El-Nino effect becomes evident. [Temporal variation in rainfall is how the amount, frequency, and intensity of precipitation change over time at a specific place.]
If we examine the rainfall received by the entire country, the El Nino effect becomes more visible. There are some states that have received very little rain and are in deficit, some states have received normal rainfall. Even within states, some districts are in deficit.
Intermittent dry spells also impact other factors, such as a rise in temperatures, with much higher maximum temperatures that do not align with the monsoon trend. All of this is attributed to the impact of El-Nino.
What is considered normal, below normal, and above normal rainfall?
IMD considers average rainfall of 10 years, to determine the variation expected during any particular monsoon season. We categorise the variation into 5 broad brackets:
Large excess (+60% OR MORE)
Excess (+20% to +59%)
Normal (+19% to -19%)
Deficient (-20% to -59%)
Large Deficient (-60% to -99%)
