Every heat event the pipeline tracked between 2021-05-01 and 2021-09-30, with how each one grew, peaked and moved. Anomalies are against the 1991–2020 baseline.
Season at a glance
Events tracked
31
Total heat burden
106.61 Mkm²·days
Longest
31days (#12)
Hottest
+22.7°C (#2)
With a heat dome
11of 31 events
A heat dome is the stricter object: a tracked heat event with a closed 500 hPa anticyclone whose influence cap overlies it, after Loikith et al. (2026). Most heatwaves are not domes, so the label is a finding and not a synonym.
ERA5 daily maximum 2 m temperature over land, against the 1991–2020 climatology (p90 in a centred 15-day window). A heatwave cell is Tx above p90 on at least 3 consecutive days.
When the events ran
Overlapping bars are concurrent events in different places, not one event counted twice: each is a separately labelled cluster of contiguous heatwave cells.
How each event evolved
Event #12 — 2021-06-27 → 2021-07-27 31 dayshigh on 13/31 d only
peak 2.12 M km² on 2021-07-07 · max +17.1 °C · mean +7.7 °C · burden 29.24 M km²·d · drift 2892 km (60.2 N 23.2 E → 37.9 N 44.4 E)
Event #9 — 2021-06-08 → 2021-07-06 29 daysheat dome · 15/29 d · Z500 +267 m
peak 2.64 M km² on 2021-06-23 · max +15.6 °C · mean +9.1 °C · burden 28.07 M km²·d · drift 3482 km (43.1 N 3.1 E → 39.0 N 44.7 E)
Event #2 — 2021-05-08 → 2021-05-25 18 daysheat dome · 10/18 d · Z500 +309 m
peak 1.36 M km² on 2021-05-13 · max +22.7 °C · mean +10.1 °C · burden 11.39 M km²·d · drift 347 km (36.5 N 43.5 E → 39.3 N 41.6 E)
Event #18 — 2021-08-07 → 2021-08-17 11 dayshigh on 2/11 d only
peak 966k km² on 2021-08-14 · max +12.3 °C · mean +6.3 °C · burden 5.60 M km²·d · drift 444 km (43.6 N 17.7 E → 40.6 N 14.1 E)
Event #15 — 2021-07-25 → 2021-08-07 14 dayshigh on 3/14 d only
peak 603k km² on 2021-07-29 · max +12.1 °C · mean +6.1 °C · burden 5.54 M km²·d · drift 508 km (43.6 N 18.4 E → 40.5 N 22.8 E)
Event #6 — 2021-05-28 → 2021-06-12 16 daysheat dome · 9/16 d · Z500 +329 m
peak 946k km² on 2021-06-04 · max +17.1 °C · mean +10.1 °C · burden 3.66 M km²·d · drift 999 km (60.7 N 8.1 E → 65.3 N 25.4 E)
Event #21 — 2021-08-24 → 2021-09-02 10 dayshigh on 1/10 d only
peak 648k km² on 2021-08-29 · max +12.4 °C · mean +5.5 °C · burden 2.75 M km²·d · drift 96 km (38.3 N 44.6 E → 39.1 N 44.2 E)
Event #1 — 2021-05-01 → 2021-05-10 10 daysheat dome · 8/9 d · Z500 +186 m
peak 601k km² on 2021-05-03 · max +14.2 °C · mean +7.8 °C · burden 2.17 M km²·d · drift 303 km (39.2 N 31.5 E → 37.0 N 29.4 E)
Event #17 — 2021-08-03 → 2021-08-17 15 dayshigh on 2/15 d only
peak 223k km² on 2021-08-13 · max +13.9 °C · mean +6.4 °C · burden 1.63 M km²·d · drift 211 km (35.5 N 6.3 E → 36.0 N 4.0 E)
Event #20 — 2021-08-16 → 2021-08-21 6 dayshigh on 2/6 d only
peak 370k km² on 2021-08-18 · max +15.0 °C · mean +8.6 °C · burden 1.47 M km²·d · drift 215 km (54.8 N 40.0 E → 54.9 N 43.4 E)
Event #3 — 2021-05-09 → 2021-05-13 5 daysheat dome · 3/5 d · Z500 +263 m
peak 423k km² on 2021-05-11 · max +12.1 °C · mean +8.8 °C · burden 1.28 M km²·d · drift 1128 km (50.7 N 14.1 E → 58.9 N 24.6 E)
Event #8 — 2021-06-07 → 2021-06-14 8 dayshigh on 2/8 d only
peak 300k km² on 2021-06-11 · max +17.0 °C · mean +10.0 °C · burden 1.22 M km²·d · drift 690 km (69.8 N 26.0 E → 64.6 N 34.8 E)
Event #23 — 2021-09-03 → 2021-09-09 7 daysheat dome · 4/7 d · Z500 +208 m
peak 348k km² on 2021-09-07 · max +11.3 °C · mean +7.2 °C · burden 1.20 M km²·d · drift 459 km (48.8 N -0.1 E → 51.8 N 4.5 E)
Event #26 — 2021-09-08 → 2021-09-12 5 daysheat dome · 4/5 d · Z500 +177 m
peak 373k km² on 2021-09-10 · max +9.3 °C · mean +6.7 °C · burden 1.13 M km²·d · drift 627 km (54.5 N 18.4 E → 54.6 N 28.2 E)
Event #13 — 2021-07-16 → 2021-07-26 11 daysheat dome · 8/11 d · Z500 +244 m
peak 170k km² on 2021-07-20 · max +10.6 °C · mean +6.7 °C · burden 1.09 M km²·d · drift 316 km (54.2 N -2.9 E → 56.9 N -4.1 E)
Event #27 — 2021-09-10 → 2021-09-17 8 dayshigh on 3/8 d only
peak 254k km² on 2021-09-14 · max +10.3 °C · mean +6.7 °C · burden 1.08 M km²·d · drift 524 km (48.0 N 18.3 E → 44.2 N 22.4 E)
Event #14 — 2021-07-24 → 2021-07-29 6 dayshigh on 1/6 d only
peak 232k km² on 2021-07-26 · max +10.2 °C · mean +7.1 °C · burden 929k km²·d · drift 310 km (62.0 N 16.9 E → 64.8 N 15.7 E)
Event #24 — 2021-09-04 → 2021-09-11 8 dayshigh on 3/8 d only
peak 192k km² on 2021-09-07 · max +10.9 °C · mean +6.7 °C · burden 760k km²·d · drift 437 km (51.0 N -4.3 E → 54.2 N -0.6 E)
Event #7 — 2021-06-06 → 2021-06-15 10 daysno overlying high
peak 191k km² on 2021-06-09 · max +8.7 °C · mean +7.0 °C · burden 677k km²·d · drift 325 km (37.3 N -7.4 E → 37.8 N -3.8 E)
Event #5 — 2021-05-25 → 2021-06-06 13 daysno overlying high
peak 160k km² on 2021-05-28 · max +10.1 °C · mean +5.7 °C · burden 660k km²·d · drift 422 km (38.3 N 40.0 E → 39.0 N 44.8 E)
Event #22 — 2021-08-26 → 2021-09-03 9 daysno overlying high
peak 129k km² on 2021-08-30 · max +9.8 °C · mean +5.8 °C · burden 612k km²·d · drift 232 km (60.5 N 5.5 E → 58.7 N 7.7 E)
Event #19 — 2021-08-08 → 2021-08-13 6 dayshigh on 2/6 d only
peak 154k km² on 2021-08-10 · max +10.7 °C · mean +7.8 °C · burden 542k km²·d · drift 178 km (56.4 N 42.1 E → 56.3 N 45.0 E)
Event #28 — 2021-09-12 → 2021-09-19 8 dayshigh on 2/8 d only
peak 121k km² on 2021-09-15 · max +10.4 °C · mean +6.2 °C · burden 537k km²·d · drift 622 km (35.8 N 1.7 E → 35.4 N 8.6 E)
Event #30 — 2021-09-23 → 2021-09-30 8 dayshigh on 4/8 d only
peak 148k km² on 2021-09-25 · max +13.2 °C · mean +7.9 °C · burden 519k km²·d · drift 520 km (36.7 N 6.7 E → 35.0 N 1.4 E)
Event #4 — 2021-05-23 → 2021-05-28 6 dayshigh on 3/6 d only
peak 135k km² on 2021-05-26 · max +11.1 °C · mean +7.2 °C · burden 501k km²·d · drift 368 km (36.8 N 29.1 E → 39.5 N 31.6 E)
Event #11 — 2021-06-16 → 2021-06-21 6 daysheat dome · 5/6 d · Z500 +267 m
peak 125k km² on 2021-06-18 · max +14.3 °C · mean +9.0 °C · burden 491k km²·d · drift 124 km (57.5 N 16.1 E → 58.5 N 17.1 E)
Event #29 — 2021-09-21 → 2021-09-26 6 dayshigh on 2/6 d only
peak 125k km² on 2021-09-24 · max +6.6 °C · mean +4.2 °C · burden 404k km²·d · drift 166 km (53.3 N 0.3 E → 54.1 N -1.9 E)
Event #25 — 2021-09-07 → 2021-09-14 8 daysheat dome · 5/8 d · Z500 +208 m
peak 114k km² on 2021-09-08 · max +9.5 °C · mean +6.3 °C · burden 398k km²·d · drift 150 km (60.4 N 10.4 E → 59.9 N 7.9 E)
Event #10 — 2021-06-09 → 2021-06-15 7 dayshigh on 2/7 d only
peak 106k km² on 2021-06-11 · max +14.6 °C · mean +9.9 °C · burden 365k km²·d · drift 375 km (64.6 N 38.9 E → 67.3 N 44.0 E)
Event #31 — 2021-09-26 → 2021-09-29 4 daysheat dome · 3/4 d · Z500 +319 m
peak 115k km² on 2021-09-28 · max +8.8 °C · mean +5.6 °C · burden 346k km²·d · drift 225 km (68.0 N 39.1 E → 67.4 N 34.1 E)
Event #16 — 2021-07-25 → 2021-07-29 5 daysno overlying high
peak 106k km² on 2021-07-27 · max +10.0 °C · mean +6.7 °C · burden 329k km²·d · drift 284 km (62.2 N 24.0 E → 64.7 N 24.8 E)
Filled area is the event footprint in km² (left axis); the solid line is the peak anomaly inside it and the dashed line the mean (right axis). The small panel is the centroid path, circles sized by area and the ring marking day one. Drift is the straight-line start-to-end distance, so a dome that wandered and returned reports a small number.