Na va-nad

Data source and script

The data come from the Météo-France daily or hourly climatological observations published on data.gouv.fr.

The script used for the calculation is available as a GitHub Gist: joseph-sch/5b6399552efa0c431b6a2bfe94a88218.

Final summary for June 18-July 3, 2026

Paris stations

Metric	Paris-Luxembourg	Paris-Montsouris
Days above 35°C	10	10
Longest run above 35°C	10 days	10 days
Run start	2026-06-18	2026-06-18
Run end	2026-06-27	2026-06-27
Daytime excess above 35°C	36.9 °C·days	24.6 °C·days
Night excess above 20°C	41.9 °C·nights	34.2 °C·nights
Highest Tmax	42.1°C	40.5°C
Highest Tmin	28.4°C	26.6°C

What the numbers show

The Météo-France hourly observations show ten consecutive days with maximum temperatures above 35°C at both Paris-Luxembourg and Paris-Montsouris, from June 18 to June 27, 2026. Paris-Luxembourg reached 42.1°C and accumulated 36.9 °C·days above 35°C, compared with 40.5°C and 24.6 °C·days at Paris-Montsouris. The nighttime burden was also greater at Luxembourg: 41.9 °C·nights above 20°C, versus 34.2 at Montsouris.

August 2003 comparison period

For comparison, the same script was run on Météo-France daily observations for July 25 to August 20, 2003.

Paris-Montsouris

Metric	August 2003	June 2026
Days above 35°C	9	10
Longest run above 35°C	9 days	10 days
Run start	2003-08-04	2026-06-18
Run end	2003-08-12	2026-06-27
Daytime excess above 35°C	28.1 °C·days	24.6 °C·days
Night excess above 20°C	35.0 °C·nights	34.2 °C·nights
Highest Tmax	39.5°C	40.5°C
Highest Tmin	25.5°C	26.6°C

Paris-Luxembourg

Metric	August 2003	June 2026
Days above 35°C	10	10
Longest run above 35°C	10 days	10 days
Run start	2003-08-03	2026-06-18
Run end	2003-08-12	2026-06-27
Daytime excess above 35°C	36.0 °C·days	36.9 °C·days
Night excess above 20°C	19.0 °C·nights	41.9 °C·nights
Highest Tmax	40.2°C	42.1°C
Highest Tmin	23.2°C	28.4°C

Comparing June 2026 with August 2003

At Paris-Montsouris, the June 2026 episode lasted ten consecutive days above 35°C, one day longer than the nine-day sequence from August 4 to August 12, 2003. Its peak was also higher, 40.5°C versus 39.5°C, but its cumulative daytime excess remained lower: 24.6 °C·days in 2026 versus 28.1 in the 2003 comparison window. The nighttime excess was similar but slightly lower in 2026, at 34.2 versus 35.0 °C·nights.

At Paris-Luxembourg, the 2026 heat wave matched the ten-day 2003 sequence. Its peak temperature was higher, 42.1°C versus 40.2°C, and both cumulative excess measures were also higher: 36.9 versus 36.0 °C·days during the day, and 41.9 versus 19.0 °C·nights at night.

Conclusion

The completed observations place the June 2026 heat wave in the same range as August 2003 by duration, with ten consecutive days above 35°C at both ground-level Paris stations. In central Paris, represented by Paris-Luxembourg, 2026 exceeded the 2003 comparison in peak temperature and nighttime heat burden. At Paris-Montsouris, however, August 2003 still produced the greater cumulative daytime excess despite its slightly shorter run. The comparison therefore does not yield a single citywide "winner": June 2026 was exceptionally long and intense in the urban core, while the severity of 2003 remained more pronounced at Montsouris by cumulative daytime excess.