No matter how you measure it, this month is the hottest June since the government started keeping weather records in 1874. The temperature has hit 90 degrees or more on 15 different days, starting June 2 and ending Tuesday. That ties a record set in 1943 for the most 90-degree days in June, and it’s more than we had for the entire summer last year. The average temperature for the month, factoring in highs and lows, is about 78.1, topping the record of an even 78, set in 1925. Those readings are for Philadelphia, where official weather records are kept.