Stroke: The presentation of unilateral weakness is highly suggestive of a stroke, particularly when combined with contralateral temperature changes, which could indicate a sensory deficit often seen in stroke patients. The sudden onset of these symptoms further supports this diagnosis.

Multiple Sclerosis (MS): MS can present with a wide range of neurological symptoms, including unilateral weakness and sensory changes such as altered temperature perception. However, the pattern of symptoms and the presence of optic neuritis, spinal cord lesions, or brainstem involvement would help differentiate MS from other diagnoses.
Peripheral Nerve Injury: Damage to a peripheral nerve can cause weakness and sensory changes, including altered temperature sensation, on the affected side. The distribution of symptoms would depend on the specific nerve injured.
Spinal Cord Injury: A spinal cord injury could result in unilateral or bilateral weakness and sensory changes, depending on the level and completeness of the injury. Contralateral temperature changes might be seen in the case of a Brown-Séquard syndrome, where there is a hemisection of the spinal cord.

Spinal Epidural Abscess: This is a medical emergency that can present with neurological deficits, including weakness and sensory changes. Fever and back pain are common accompanying symptoms. Prompt diagnosis and treatment are crucial to prevent permanent neurological damage.
Subarachnoid Hemorrhage: Although typically presenting with a severe headache, subarachnoid hemorrhage can also cause focal neurological deficits, including weakness. The sudden onset of symptoms and potential for rapid deterioration make this a critical diagnosis not to miss.
Cervical Spine Injury: Especially in the context of trauma, a cervical spine injury could lead to neurological deficits. It's crucial to immobilize the cervical spine until injury can be ruled out to prevent further damage.

Syringomyelia: A condition characterized by the formation of a fluid-filled cavity or syrinx within the spinal cord, which can expand and elongate over time, damaging the spinal cord. It can cause unilateral weakness and sensory changes, including loss of temperature sensation, typically in a cape-like distribution.
Neurosarcoidosis: Sarcoidosis can affect the nervous system, leading to a variety of symptoms, including weakness and sensory changes. While rare, it's an important consideration in patients with known sarcoidosis or when other diagnoses are ruled out.