May in Cuautitlán Izcalli, Mexico, brings average daily highs of 28°C and overnight lows of 14°C in the 2016–2025 historical record. Light clothing is a useful starting point, with room in the plan to pause indoors. Decide how much walking to fit into each day using the local forecast, rather than treating the monthly average as a limit.
In the record, at least 1 mm of rain or snow falls on 9 of 31 days on average, a daily chance of 30%. Leave some freedom to swap an outdoor day with a sheltered one. There is no need to read the average as a fixed number of lost days; it says nothing about how long rain lasts on each occasion.
The calculated day length, sunrise to sunset, averages about 13 hours. Sunshine averages 12 hours a day. Use the daylight window to plan the length of excursions, and check local sunrise and sunset times for the dates of your stay. Sunshine is a separate measure, and those hours need not arrive in one uninterrupted stretch.
For time in town, cluster a few stops together and leave the rest of the day open. Check transport and opening hours for any plans that run late.
June has an average daily high of 26°C, 2°C lower than May. Its historical rain-day chance is 50%, compared with 30% this month. If your dates are flexible, compare those trade-offs with the kind of days you want. Neither set of averages predicts the conditions of one particular holiday.