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: 2025-06-17T17:50:36Z in 0.14s

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
32025-03-3020610223.28
42023-03-318576472.87
52024-05-088539336
62025-04-288486522.98
72025-03-1420463326.85
82020-04-128456744.96
92015-05-168404365.22
102025-03-1520375780.16

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

Generated at: 2025-06-17T17:50:36Z in 0.14s

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
82018-05-01865789.28
92016-10-04868354.55
102015-06-03871486.1