Although the weather is unpredictable in Glasgow, it is usually the hottest in July and August when it reaches highs of about 20 °C. Meanwhile, in December and January, the weather is the coldest, reaching lows of about 0 °C.
Glasgow does not guarantee great weather; however, from May through June, it is usually sunny and pleasant. In July and the beginning of August, there is usually nice, comfortable weather. Bear in mind that even if it were to rain in Glasgow, it is such a charming place that there are still plenty of activities to keep you occupied.