Iowa frost dates: B
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Badger | Apr 28 | Oct 8 | 163 d | 5a |
| Bagley | May 2 | Oct 3 | 154 d | 5a |
| Baldwin | Apr 25 | Oct 14 | 172 d | 5a |
| Bancroft | May 4 | Oct 1 | 150 d | 5a |
| Barnes City | Apr 21 | Oct 16 | 178 d | 5b |
| Barnum | Apr 28 | Oct 8 | 163 d | 5a |
| Batavia | Apr 27 | Oct 12 | 168 d | 5b |
| Battle Creek | May 1 | Oct 1 | 153 d | 5a |
| Baxter | Apr 22 | Oct 17 | 178 d | 5b |
| Bayard | May 2 | Oct 3 | 154 d | 5a |
| Beacon | Apr 21 | Oct 16 | 178 d | 5b |
| Beaman | Apr 29 | Oct 9 | 163 d | 5a |
| Beaver | Apr 28 | Oct 12 | 167 d | 5a |
| Bedford | Apr 24 | Oct 15 | 174 d | 5b |
| Belle Plaine | Apr 28 | Oct 10 | 165 d | 5a |
| Bellevue | Apr 25 | Oct 16 | 174 d | 5a |
| Belmond | Apr 30 | Oct 10 | 163 d | 5a |
| Bennett | Apr 21 | Oct 15 | 177 d | 5a |
| Benton | Apr 25 | Oct 12 | 170 d | 5b |
| Bernard | Apr 28 | Oct 10 | 165 d | 5a |
| Berwick | Apr 23 | Oct 15 | 175 d | 5b |
| Bettendorf | Apr 19 | Oct 22 | 186 d | 5b |
| Bevington | Apr 24 | Oct 12 | 171 d | 5b |
| Birmingham | Apr 26 | Oct 13 | 170 d | 5b |
| Blairsburg | May 3 | Oct 2 | 152 d | 5a |
| Blairstown | Apr 28 | Oct 10 | 165 d | 5a |
| Blakesburg | Apr 24 | Oct 16 | 175 d | 5b |
| Blanchard | Apr 25 | Oct 11 | 169 d | 5b |
| Blencoe | May 1 | Oct 3 | 155 d | 5a |
| Blockton | Apr 24 | Oct 14 | 173 d | 5b |
| Bloomfield | Apr 16 | Oct 22 | 189 d | 5b |
| Blue Grass | Apr 19 | Oct 22 | 186 d | 5b |
| Bode | Apr 27 | Oct 9 | 165 d | 5a |
| Bonaparte | Apr 26 | Oct 13 | 170 d | 6a |
| Bondurant | Apr 23 | Oct 15 | 175 d | 5b |
| Boone | Apr 28 | Oct 12 | 167 d | 5a |
| Booneville | Apr 18 | Oct 20 | 185 d | 5b |
| Bouton | Apr 25 | Oct 10 | 168 d | 5a |
| Boxholm | Apr 28 | Oct 12 | 167 d | 5a |
| Boyden | May 5 | Sep 28 | 146 d | 5a |
| Braddyville | Apr 25 | Oct 11 | 169 d | 5b |
| Bradford | Apr 28 | Oct 10 | 165 d | 5a |
| Bradgate | Apr 27 | Oct 9 | 165 d | 5a |
| Brandon | May 3 | Oct 3 | 153 d | 5a |
| Brayton | Apr 30 | Oct 2 | 155 d | 5a |
| Breda | Apr 27 | Oct 10 | 166 d | 5a |
| Bridgewater | Apr 25 | Oct 12 | 170 d | 5b |
| Brighton | Apr 28 | Oct 11 | 166 d | 5b |
| Bristow | Apr 27 | Oct 8 | 164 d | 5a |
| Britt | Apr 29 | Oct 7 | 161 d | 5a |
| Bronson | Apr 29 | Oct 7 | 161 d | 5a |
| Brooklyn | Apr 28 | Oct 10 | 165 d | 5a |
| Brunsville | Apr 30 | Oct 4 | 157 d | 5a |
| Bryant | Apr 13 | Oct 26 | 196 d | 5a |
| Buckeye | Apr 28 | Oct 10 | 165 d | 5a |
| Buckingham | Apr 30 | Oct 9 | 162 d | 5a |
| Buffalo | Apr 19 | Oct 22 | 186 d | 5b |
| Buffalo Center | Apr 30 | Oct 7 | 160 d | 5a |
| Burlington | Apr 15 | Oct 20 | 188 d | 6a |
| Burnside | Apr 28 | Oct 8 | 163 d | 5a |
| Burt | Apr 30 | Oct 6 | 159 d | 5a |
| Bussey | Apr 24 | Oct 16 | 175 d | 5b |