Iowa frost dates: M
| City | Last frost | First frost | Season | Zone |
|---|---|---|---|---|
| Macedonia | Apr 23 | Oct 14 | 174 d | 5b |
| Macksburg | Apr 30 | Oct 3 | 156 d | 5b |
| Madrid | Apr 23 | Oct 14 | 174 d | 5b |
| Magnolia | Apr 29 | Oct 8 | 162 d | 5b |
| Malcom | May 3 | Oct 6 | 156 d | 5a |
| Mallard | Apr 27 | Oct 7 | 163 d | 5a |
| Malvern | Apr 23 | Oct 11 | 171 d | 5b |
| Manchester | May 3 | Oct 4 | 154 d | 5a |
| Manilla | Apr 27 | Oct 11 | 167 d | 5a |
| Manly | Apr 29 | Oct 7 | 161 d | 5a |
| Manning | Apr 27 | Oct 10 | 166 d | 5a |
| Manson | Apr 26 | Oct 10 | 167 d | 5a |
| Mapleton | May 3 | Oct 1 | 151 d | 5a |
| Maquoketa | Apr 25 | Oct 14 | 172 d | 5a |
| Marathon | Apr 30 | Oct 5 | 158 d | 5a |
| Marble Rock | Apr 30 | Oct 6 | 159 d | 5a |
| Marcus | May 4 | Oct 4 | 153 d | 5a |
| Marengo | Apr 28 | Oct 9 | 164 d | 5a |
| Marion | Apr 28 | Oct 12 | 167 d | 5a |
| Marne | Apr 30 | Oct 2 | 155 d | 5b |
| Marquette | Apr 28 | Oct 12 | 167 d | 5a |
| Marshalltown | Apr 28 | Oct 7 | 162 d | 5a |
| Martelle | Apr 27 | Oct 13 | 169 d | 5a |
| Martensdale | Apr 24 | Oct 12 | 171 d | 5b |
| Martinsburg | Apr 24 | Oct 15 | 174 d | 5b |
| Mason City | Apr 29 | Oct 7 | 161 d | 5a |
| Masonville | May 3 | Oct 4 | 154 d | 5a |
| Massena | Apr 25 | Oct 12 | 170 d | 5b |
| Matlock | May 5 | Sep 28 | 146 d | 5a |
| Maurice | Apr 30 | Oct 3 | 156 d | 5a |
| Maxwell | Apr 24 | Oct 12 | 171 d | 5b |
| Maynard | Apr 27 | Oct 13 | 169 d | 5a |
| Mc Callsburg | Apr 24 | Oct 12 | 171 d | 5a |
| Mc Causland | Apr 22 | Oct 16 | 177 d | 5b |
| Mc Clelland | Apr 18 | Oct 21 | 186 d | 5b |
| Mc Gregor | Apr 28 | Oct 12 | 167 d | 5a |
| Mc Intire | Apr 30 | Oct 9 | 162 d | 5a |
| Mechanicsville | Apr 21 | Oct 15 | 177 d | 5a |
| Mediapolis | Apr 8 | Oct 29 | 204 d | 5b |
| Melbourne | Apr 28 | Oct 7 | 162 d | 5b |
| Melcher Dallas | Apr 20 | Oct 19 | 182 d | 5b |
| Melrose | Apr 18 | Oct 23 | 188 d | 5b |
| Melvin | May 1 | Oct 7 | 159 d | 5a |
| Menlo | May 2 | Oct 3 | 154 d | 5b |
| Meriden | May 4 | Oct 4 | 153 d | 5a |
| Merrill | Apr 30 | Oct 4 | 157 d | 5a |
| Meservey | Apr 29 | Oct 9 | 163 d | 5a |
| Middle Amana | Apr 28 | Oct 9 | 164 d | 5b |
| Middletown | Apr 15 | Oct 20 | 188 d | 6a |
| Miles | Apr 25 | Oct 16 | 174 d | 5a |
| Milford | May 1 | Oct 6 | 158 d | 5a |
| Millersburg | Apr 28 | Oct 9 | 164 d | 5b |
| Millerton | Apr 21 | Oct 19 | 181 d | 5b |
| Milo | Apr 24 | Oct 12 | 171 d | 5b |
| Milton | Apr 26 | Oct 13 | 170 d | 5b |
| Minburn | Apr 25 | Oct 10 | 168 d | 5a |
| Minden | Apr 23 | Oct 14 | 174 d | 5b |
| Mineola | Apr 23 | Oct 11 | 171 d | 5b |
| Mingo | Apr 22 | Oct 17 | 178 d | 5b |
| Missouri Valley | Apr 29 | Oct 8 | 162 d | 5b |
| Mitchellville | Apr 21 | Oct 15 | 177 d | 5b |
| Modale | Apr 22 | Oct 17 | 178 d | 5b |
| Mondamin | May 1 | Oct 3 | 155 d | 5b |
| Monmouth | Apr 25 | Oct 14 | 172 d | 5a |
| Monona | May 1 | Oct 3 | 155 d | 5a |
| Monroe | Apr 21 | Oct 15 | 177 d | 5b |
| Montezuma | May 3 | Oct 6 | 156 d | 5b |
| Monticello | May 1 | Oct 4 | 156 d | 5a |
| Montour | Apr 30 | Oct 9 | 162 d | 5a |
| Montpelier | Apr 18 | Oct 24 | 189 d | 5b |
| Montrose | Apr 10 | Oct 27 | 200 d | 6a |
| Moorhead | Apr 25 | Oct 12 | 170 d | 5b |
| Moorland | Apr 28 | Oct 8 | 163 d | 5a |
| Moravia | Apr 18 | Oct 23 | 188 d | 5b |
| Morley | Apr 27 | Oct 13 | 169 d | 5a |
| Morning Sun | Apr 14 | Oct 24 | 193 d | 5b |
| Morrison | Apr 29 | Oct 9 | 163 d | 5a |
| Moscow | Apr 18 | Oct 22 | 187 d | 5b |
| Moulton | Apr 28 | Oct 14 | 169 d | 5b |
| Mount Auburn | May 3 | Oct 3 | 153 d | 5a |
| Mount Ayr | Apr 25 | Oct 12 | 170 d | 5b |
| Mount Pleasant | Apr 30 | Oct 10 | 163 d | 5b |
| Mount Sterling | Apr 26 | Oct 13 | 170 d | 6a |
| Mount Union | Apr 30 | Oct 10 | 163 d | 5b |
| Mount Vernon | Apr 28 | Oct 12 | 167 d | 5a |
| Moville | Apr 29 | Oct 7 | 161 d | 5a |
| Murray | Apr 29 | Oct 9 | 163 d | 5b |
| Muscatine | Apr 24 | Oct 14 | 173 d | 5b |
| Mystic | Apr 18 | Oct 23 | 188 d | 5b |