月ごとの値
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室蘭（胆振地方) 1998年（月ごとの値） 詳細（気温・蒸気圧・湿度）
| 月 | 気温(℃) | 蒸気圧 (hPa) | 湿度(％) | ||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 日平均 | 最高気温 | 最低気温 | 各階級の日数（平均） | 各階級の日数（最低） | 各階級の日数（最高） | ||||||||||||||||||
| 平均 | 平均 | 最高 | 最低 | 平均 | 最低 | 最高 | ＜0℃ | ≧25℃ | ＜0℃ | ≧25℃ | ＜0℃ | ≧25℃ | ≧30℃ | ≧35℃ | 平均 | 平均 | 最小 | ||||||
| 値 | 日 | 値 | 日 | 値 | 日 | 値 | 日 | 値 | 日 | ||||||||||||||
| -4.3 | -1.7 | 3.3 | 18 | -6.3 | 08 | -6.6 | -11.4 | 07 | -0.6 | 18 | 30 | 0 | 31 | 0 | 21 | 0 | 0 | 0 | 3.1 | 67 | 40 | 14 | |
| -2.2 | 0.3 | 5.4 | 20 | -4.7 | 04 | -4.8 | -10.9 | 07 | -0.1 | 27 | 21 | 0 | 28 | 0 | 12 | 0 | 0 | 0 | 3.8 | 70 | 25 | 21 | |
| 2.0 | 5.7 | 12.1 | 28 | -0.9 | 16 | -1.2 | -4.6 | 10 | 3.6 | 29 | 6 | 0 | 22 | 0 | 1 | 0 | 0 | 0 | 4.9 | 69 | 26 | 25 | |
| 6.8 | 10.9 | 21.7 | 21 | 3.6 | 02 | 3.5 | -2.2 | 01 | 13.0 | 21 | 0 | 0 | 3 | 0 | 0 | 0 | 0 | 0 | 7.8 | 78 | 22 | 03 | |
| 11.0 | 15.5 | 25.7 | 16 | 8.7 | 01 | 7.5 | 2.9 | 11 | 12.3 | 18 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 10.2 | 78 | 26 | 26 | |
| 12.6 | 15.5 | 23.9 | 28 | 9.3 | 03 | 10.7 | 7.0 | 05 | 15.8 | 28 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 13.4 | 91 | 55 | 18 | |
| 17.7 | 20.3 | 24.8 | 09 | 17.0 | 11 | 16.1 | 13.7 | 16 | 18.8 | 27 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 18.7 | 92 | 63 | 05 | |
| 19.5 | 22.0 | 26.2 | 25 | 18.6 | 03 | 17.9 | 15.8 | 08 | 19.9 | 25 | 0 | 0 | 0 | 0 | 0 | 4 | 0 | 0 | 21.1 | 93 | 57 | 09 | |
| 19.4 | 22.5 | 26.5 | 11 | 18.4 | 24 | 17.1 | 12.6 | 29 | 20.0 | 12 | 0 | 0 | 0 | 0 | 0 | 3 | 0 | 0 | 19.7 | 87 | 43 | 28 | |
| 14.4 | 17.4 | 21.6 | 18 | 13.7 | 23* | 11.5 | 8.1 | 27 | 16.1 | 15 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 12.7 | 76 | 35 | 31 | |
| 4.6 | 7.7 | 17.6 | 04 | -1.1 | 21 | 1.5 | -5.3 | 21 | 7.8 | 01 | 3 | 0 | 11 | 0 | 3 | 0 | 0 | 0 | 6.5 | 73 | 41 | 19 | |
| -0.2 | 2.3 | 8.9 | 08 | -3.0 | 31 | -2.5 | -6.9 | 31 | 3.1 | 13 | 19 | 0 | 26 | 0 | 9 | 0 | 0 | 0 | 4.4 | 72 | 45 | 19* | |