Top 10 SPC Outlooks by Size

New: Scroll down to see the top 10 smallest outlooks by size!

The IEM attempts a robust archive of SPC outlooks. These outlooks have changed methodologies and threshold meanings over the years. You are strongly encouraged to set a start year to limit the data to a given period. The listing only inludes one outlook for a given canonical date.

This app can be slow to generate! For common outlook types, the backend database query can take a number of seconds to complete. The computed area is done within the US National Atlas Equal Area (EPSG:9311).

Related: Top 10 MCDs by Size SPC Outlook Shapefile Download

Inclusive Start Year: Select Day: Select Threshold:

Top 10 Largest Day: 3 Category: CATEGORICAL Threshold: ENH

Generated at: 2026-04-11T21:31:52Z in 0.16s

JSON Webservice for the data below:
https://mesonet.agron.iastate.edu/json/spc_bysize.py?day=3&threshold=ENH&category=CATEGORICAL&syear=1987&sort=desc

Rank Canonical Outlook Date Cycle Hour UTCSize (sq km)SPC Link/Image
12025-04-0220781251.39
22022-04-138614243.56
32025-03-308610223.28
42023-03-318576472.87
52024-05-088539336
62026-03-1520535591.05
72025-04-288486522.98
82025-03-1420463326.85
92020-04-128456744.96
102015-05-168404365.22

Top 10 Smallest Day: 3 Category: CATEGORICAL Threshold: ENH

Generated at: 2026-04-11T21:31:52Z in 0.16s

JSON Webservice for the data below:
https://mesonet.agron.iastate.edu/json/spc_bysize.py?day=3&threshold=ENH&category=CATEGORICAL&syear=1987&sort=asc

Rank Canonical Outlook Date Cycle Hour UTCSize (sq km)SPC Link/Image
12020-04-13841883.53
22025-04-202044402.96
32018-03-20848874.47
42022-04-29850472.17
52017-04-06850814.85
62025-06-172052894.82
72021-04-09855283.99
82026-04-032063131.49
92018-05-01865789.28
102025-08-082066957.47