Wetterstationen des Deutschen Wetterdienstes (DWD)
| Stationsname (Ort) | Seehöhe | Bundesland |
| Olbersleben | 160 m | TH |
| Oldenborstel | 30 m | SH |
| Oldenbrok | 1 m | NI |
| Oldenburg | 11 m | NI |
| Oldenburg (A) | 5 m | NI |
| Oldenburg i. Holst. | 15 m | SH |
| Oldenburg i. Holst.-Lübbersdorf | 5 m | SH |
| Oldenburg in Holstein | 6 m | SH |
| Oldenburg/Oldenb.-Haarentor | 5 m | NI |
| Oldendorf a.d. Göhrde | 60 m | NI |
| Oldendorf, Stade | 15 m | NI |
| Oldenstadt | 40 m | NI |
| Oldesloe, Bad | 15 m | SH |
| Oldesloe, Bad (PH) | 15 m | SH |
| Oldisleben | 129 m | TH |
| Oldisleben (PH) | 130 m | TH |
| Oldsum | 3 m | SH |
| Olfen | 49 m | NW |
| Olmscheid | 340 m | RP |
| Olpe | 305 m | NW |
| Olpe/Biggesee | 320 m | NW |
| Olpenitz b. Kappeln | 15 m | SH |
| Olsberg | 340 m | NW |
| Olsberg-Brunskappel | 442 m | NW |
| Olsdorf | 328 m | RP |
| Ommersheim | 320 m | SL |
| Opfenbach | 595 m | BY |
| Opladen | 50 m | NW |
| Oppach | 320 m | SN |
| Oppau (Kreis Ludwigshafen) | 92 m | RP |
| Oppenau | 315 m | BW |
| Oppenau | 280 m | BW |
| Oppenau Oberes Renchtal | 234 m | BW |
| Oppenheim | 85 m | RP |
| Oppenheim (DLR RLP) | 128 m | RP |
| Oppenheim (PH) | 120 m | RP |
| Oppenweiler | 260 m | BW |
| Opperhausen | 120 m | NI |
| Oppin | 106 m | ST |
| Oppurg | 240 m | TH |
| Oranienbaum | 63 m | ST |
| Oranienbaum (PH) | 65 m | ST |
| Oranienburg | 35 m | BB |
| Oranienburg (Schleuse) | 38 m | BB |
| Orb, Bad | 230 m | HE |
| Orb, Bad (PH) | 190 m | HE |
| Orlamünde | 280 m | TH |
| Orlishausen | 141 m | TH |
| Orlishausen (PH) | 140 m | TH |
| Orsenhausen | 520 m | BW |