Iowa frost dates: S
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Sabula | May 2 | Oct 7 | 158 d | 5a |
| Sac City | Apr 30 | Oct 6 | 159 d | 5a |
| Saint Ansgar | Apr 30 | Oct 9 | 162 d | 5a |
| Saint Anthony | Apr 24 | Oct 12 | 171 d | 5a |
| Saint Charles | Apr 30 | Oct 3 | 156 d | 5b |
| Saint Donatus | Apr 25 | Oct 16 | 174 d | 5a |
| Saint Lucas | May 4 | Oct 4 | 153 d | 5a |
| Saint Marys | Apr 24 | Oct 12 | 171 d | 5b |
| Saint Olaf | May 8 | Oct 1 | 146 d | 5a |
| Saint Paul | Apr 17 | Oct 22 | 188 d | 6a |
| Salem | Apr 30 | Oct 10 | 163 d | 6a |
| Salix | Apr 29 | Oct 5 | 159 d | 5a |
| Sanborn | May 1 | Oct 7 | 159 d | 5a |
| Scarville | Apr 30 | Oct 7 | 160 d | 5a |
| Schaller | Apr 25 | Oct 13 | 171 d | 5a |
| Schleswig | Apr 27 | Oct 11 | 167 d | 5a |
| Scranton | Apr 26 | Oct 9 | 166 d | 5a |
| Searsboro | May 3 | Oct 6 | 156 d | 5b |
| Selma | Apr 26 | Oct 13 | 170 d | 5b |
| Sergeant Bluff | Apr 29 | Oct 7 | 161 d | 5a |
| Seymour | Apr 21 | Oct 19 | 181 d | 5b |
| Shambaugh | Apr 25 | Oct 11 | 169 d | 5b |
| Shannon City | Apr 28 | Oct 11 | 166 d | 5b |
| Sharpsburg | Apr 24 | Oct 15 | 174 d | 5b |
| Sheffield | Apr 29 | Oct 9 | 163 d | 5a |
| Shelby | Apr 27 | Oct 9 | 165 d | 5b |
| Sheldahl | Apr 19 | Oct 18 | 182 d | 5b |
| Sheldon | May 5 | Sep 28 | 146 d | 5a |
| Shell Rock | Apr 27 | Oct 8 | 164 d | 5a |
| Shellsburg | May 3 | Oct 3 | 153 d | 5a |
| Shenandoah | Apr 20 | Oct 17 | 180 d | 5b |
| Sherrill | Apr 19 | Oct 21 | 185 d | 5a |
| Sibley | May 5 | Oct 3 | 151 d | 4b |
| Sidney | Apr 19 | Oct 19 | 183 d | 5b |
| Sigourney | Apr 24 | Oct 15 | 174 d | 5b |
| Silver City | Apr 23 | Oct 11 | 171 d | 6a |
| Sioux Center | Apr 30 | Oct 3 | 156 d | 5a |
| Sioux City | Apr 29 | Oct 7 | 161 d | 5a |
| Sioux Rapids | Apr 30 | Oct 5 | 158 d | 5a |
| Slater | Apr 26 | Oct 12 | 169 d | 5b |
| Sloan | Apr 29 | Oct 5 | 159 d | 5a |
| Smithland | May 3 | Oct 1 | 151 d | 5a |
| Soldier | Apr 25 | Oct 12 | 170 d | 5b |
| Solon | Apr 27 | Oct 11 | 167 d | 5b |
| Somers | Apr 26 | Oct 10 | 167 d | 5a |
| South Amana | Apr 28 | Oct 9 | 164 d | 5a |
| South English | Apr 24 | Oct 15 | 174 d | 5b |
| Spencer | May 1 | Oct 3 | 155 d | 5a |
| Sperry | Apr 8 | Oct 29 | 204 d | 6a |
| Spillville | May 3 | Oct 7 | 157 d | 4b |
| Spirit Lake | Apr 28 | Oct 11 | 166 d | 5a |
| Spragueville | Apr 25 | Oct 14 | 172 d | 5a |
| Springbrook | Apr 25 | Oct 16 | 174 d | 5a |
| Springville | Apr 27 | Oct 13 | 169 d | 5a |
| Stacyville | Apr 30 | Oct 9 | 162 d | 5a |
| Stanhope | May 3 | Oct 2 | 152 d | 5a |
| Stanley | May 4 | Oct 1 | 150 d | 5a |
| Stanton | Apr 24 | Oct 13 | 172 d | 5b |
| Stanwood | Apr 21 | Oct 15 | 177 d | 5a |
| State Center | Apr 24 | Oct 12 | 171 d | 5a |
| Steamboat Rock | Apr 27 | Oct 10 | 166 d | 5a |
| Stockport | Apr 26 | Oct 13 | 170 d | 6a |
| Stockton | Apr 18 | Oct 22 | 187 d | 5b |
| Storm Lake | Apr 25 | Oct 13 | 171 d | 5a |
| Story City | Apr 26 | Oct 8 | 165 d | 5a |
| Stout | Apr 29 | Oct 9 | 163 d | 5a |
| Stratford | May 3 | Oct 2 | 152 d | 5a |
| Strawberry Point | May 8 | Oct 1 | 146 d | 4b |
| Stuart | May 2 | Oct 3 | 154 d | 5b |
| Sully | May 3 | Oct 6 | 156 d | 5b |
| Sumner | Apr 29 | Oct 9 | 163 d | 5a |
| Superior | Apr 28 | Oct 11 | 166 d | 5a |
| Sutherland | Apr 29 | Oct 10 | 164 d | 5a |
| Swaledale | May 3 | Oct 1 | 151 d | 5a |
| Swan | Apr 21 | Oct 15 | 177 d | 5b |
| Swea City | May 4 | Oct 1 | 150 d | 5a |
| Swedesburg | Apr 30 | Oct 10 | 163 d | 5b |
| Swisher | Apr 27 | Oct 11 | 167 d | 5a |