Everything in these twelve lines hangs on one comparison, and Edward Thomas puts it first: "Like the touch of rain she was." The word order is slightly unusual. The simile arrives at the front and "she was" trails behind it, as if the woman can only be described through a sensation. The tense matters too. Before we learn anything else, she is already in the past, like a shower that has come and gone.
The first stanza makes that sensation physical. Rain lands "on a man's flesh and hair and eyes," a list strung together with plain "and"s, so that we feel the drops arriving one after another. The man isn't sheltering or complaining. He has been caught by a joy that "has taken him by surprise." The surprise is the point. This is not a love planned or earned, but one that falls on you unasked, like weather.
The second stanza turns that image into a paradox. The walker "burns" with love of the storm, so fire comes out of water, and then "he sings, he laughs." Then the speaker interrupts himself with a conversational aside, "well I know how," and the poem changes. What looked like a general observation turns out to be memory, and the speaker has been that man. The stanza pivots on "But forgets when he returns." The ordinary walker dries off, goes home, and the delight fades. The speaker insists on the opposite: "As I shall not forget her 'Go now.'" This is the only direct speech in the poem, the only moment the woman's own voice breaks in. After so much sensuous description, two one-syllable words in quotation marks are startlingly blunt, and they sound like something actually remembered. The rhyme helps, because "how" and "now" chime across the stanza and tie his knowledge of joy to the moment it ended.
In the final stanza the imagery moves from weather to architecture: "Those two words shut a door / Between me and the blessed rain." Rain is open, outdoors, beyond anyone's control, while a door is man-made and final. "Blessed" gives the rain something close to the quality of grace, a gift never quite deserved. The line itself is almost all monosyllables, with hard stops on "shut" and "door," and it nearly sounds like a latch clicking. There is also a quiet inversion. The walker in stanza two chooses to come home and forgets. The speaker has no such choice, because the door has been closed for him. The last two lines move from past to future, "was never shut before / And will not open again," and skip any present tense, as grief often does. The poem gives no reason for the command and no sign of blame or self-pity. We are given only what it did.
The form suits that restraint. Three quatrains rhyme ABAB, and the lines are short, with roughly four beats each, loose enough to sound like speech and tight enough to feel like a song. Most of the rhymes are full: "burns" and "returns," "how" and "now," "door" and "before." The first stanza's pairing is looser, and "rain" and "again" in the last stanza depend on how you say the second word. The poem ends on that near-echo, which feels right. The rain comes back in the sound but not in life.
Thomas is known for plain-spoken poems about walking and the countryside, and this one shows why that plainness could be so effective. He never writes "I loved her" or "I am heartbroken." He lets a small, physical experience, being touched by rain, carry the whole emotional weight, and he lets a brief, ordinary command carry the loss. The poem also sets forgetting against remembering. The happy walker forgets, but the poem exists because the speaker will not. In just twelve lines it shows that joy and its ending can both arrive as suddenly as weather, and that the second can outlast the first.