Hi, this is Ray.

I want to start with a specific summer from a few years ago that I now recognize as a case study in what NOT to do. I had committed to a serious learning project that summer. I told myself the heat wouldn't affect me. I was disciplined. I could push through. My apartment had AC that struggled to keep up but technically worked. I would just do what I'd always done… sit down at my desk, put in the hours, produce the results.

By late July, I was in genuine trouble with the project. My afternoon sessions were producing almost nothing. Material I understood clearly in June had become slippery. My focus fragmented within 20 minutes of sitting down. I blamed myself for lack of discipline. I lectured myself about being tougher than the heat. I drank more coffee. I tried harder. None of it worked. By August, I was so far behind on the project that I was doing damage-control rather than actual learning.

The problem wasn't my discipline. The problem was that I had been treating the summer heat as a psychological obstacle when it was actually a physiological one. My brain was operating in conditions that measurably degraded its capacity to encode, consolidate, and retrieve information. Every hour I spent trying to push through was an hour of impaired cognitive performance being applied to a project that needed high-quality cognitive performance. The willpower I was throwing at the problem couldn't compensate for the underlying biology.

I've written before in this newsletter about temperature and cognition, and about handling extreme weather. What I want to do today is give you the specific summer playbook… the practical strategies for learners who need to sustain serious cognitive work through hot months without waiting for autumn to make actual progress. Because the research is genuinely clear about what works, and understanding it changes what you do differently between June and September. Let's get into it.

Running more campaigns won't move the needle. Building the right strategy will.

HubSpot Academy's Digital Marketing Certification gives you the foundation to make that happen. In just over 3 hours, you'll cover consumer behavior, ethical marketing, SEO, content, email, social media, paid ads, and AI — the full stack, in one course.

Walk away with:

Free. No credit card. Shareable on LinkedIn the day you finish.

Join 200,000+ professionals who have advanced their career with HubSpot Academy — get certified today.

Get Certified Free

Let me start with what the science actually shows about summer heat and cognitive function, because the effects are more substantial than most learners realize.

According to a recent 2025 study of summer classroom effects, Jose Ali et al performed a 2-week intervention study in two elementary school classrooms in Costa Rica and observed that 11-year-olds students, whose neutral temperature was approximately 27°C, performed considerably faster on verbal and logical thinking tasks at lower temperatures. Haverinen et al reported that ventilation rates in the range of 0.9-7.1 L/s per person were positively associated with students' math scores, increasing by 11 points for each additional liter per second per person. Additionally, within the observed range of 20–25°C, performance improved by 12–13 points for every 1°C decrease in temperature. Read that carefully. Twelve to thirteen points of measurable performance improvement for every 1°C decrease. This isn't a subtle effect. Every degree above optimal is measurably degrading learning outcomes.

The physiological threshold is worth knowing. According to research on hyperthermia and cognitive performance, The existence of an inverted U-shaped relationship between hyperthermia development and cognitive performance is suggested, and highlights core temperatures of ~38.5 °C as the potential 'threshold' for hyperthermia-induced negative cognitive performance. Read this. Core body temperature of 38.5°C is when things really fall apart. But performance degrades well before that threshold in a dose-dependent way. You don't have to reach medical hyperthermia to experience the cognitive effects… the degradation happens as you approach the threshold.

The specific finding that changed how I think about this comes from research on cooling strategies. According to a systematic review, pre-cooling appears the most effective cooling method for maintaining cognitive performance under heat stress. The specific timing matters. Cooling that happens BEFORE you're trying to work in the heat is more effective than cooling during or after. This has direct practical implications for how you should structure summer study sessions.

Weather-daily's summary of the research puts the practical picture clearly. According to their analysis, the research on heat and cognition doesn't suggest that people become incapable of thought in summer heat … it suggests that the quality and speed of thinking degrades in measurable, consistent, dose-dependent ways as temperature rises. The effect is modest at moderate temperatures and substantial at high temperatures, and it operates across every cognitive domain that has been studied. This is the honest picture. You're not helpless in summer heat… you're impaired. The impairment is real, measurable, and dose-dependent. The learners who acknowledge this and work with it produce dramatically better results than the learners who pretend it isn't happening.

Summer heat presents specific challenges that other environmental conditions don't. Understanding these helps you address them specifically.

Sustained duration. Winter cold you can escape by staying inside. Summer heat, especially in poorly-cooled spaces, is a sustained condition that lasts weeks or months. Your body has to operate under thermal stress for extended periods, which produces cumulative effects that acute exposure doesn't.

Sleep degradation. Hot nights degrade sleep quality, which then compounds daytime cognitive impairment. This is the specific summer trap… your daytime performance is impaired because of the heat AND because your sleep the night before was impaired because of the heat. Both effects compound.

Dehydration compounding. As I've covered in previous newsletters, even mild dehydration significantly impairs cognition. Summer heat produces increased water loss through sweating, which means the baseline hydration challenge is harder. Learners who barely maintain hydration in cooler months often become mildly dehydrated in summer without noticing.

Motivation degradation. As one summary put it, participants were required to exert more effort in completing the task, while frustration increased, which correlated with decreased satisfaction. Working in heat isn't just cognitively harder… it feels psychologically worse. The frustration itself becomes a factor that undermines sustained effort.

Impaired self-monitoring. According to the same research, heat impairs your ability to accurately assess your own state. You don't realize how impaired you are, which means you make worse decisions about when to push and when to rest. In Zelda terms, this is like your health bar being lower than the display shows… you're closer to failure than you think.

Okay, the practical part. Based on the research and my own experience navigating multiple hot summers with serious learning projects, here's the specific playbook.

Schedule your hardest cognitive work for cool morning hours. This is the highest-leverage intervention available. According to research on temperature and cognition, Schedule cognitively demanding work for cooler periods. Morning, when temperatures haven't peaked and the body hasn't accumulated a full day's heat stress, is when cognitive performance is likely to be best. The specific move: identify the coolest 2-3 hours of your day, usually 6-10 AM. Put your most demanding learning work in that window. Save less-demanding tasks (review, familiar material, administrative work) for the hot afternoon hours.

Pre-cool before demanding sessions. As the research showed, pre-cooling is the most effective cooling strategy. Practically, this means taking specific steps to cool your body BEFORE sitting down to study, not just during. A cold shower before a difficult session. Cold water on your neck and wrists. Time in an air-conditioned space for 15 minutes before starting demanding work. The pre-cooling extends the window during which you can perform cognitively before the heat catches up.

Cool your workspace specifically for study times. You don't have to keep your home at optimal temperature all day. Cool your study space specifically for the hours you'll be working in it. Air conditioning that runs for the two hours of your morning study session is a manageable expense. Air conditioning that runs 24/7 might not be. The pattern of running cooling specifically for cognitive work times captures most of the benefit at fraction of the cost.

Hydrate more aggressively than you think you need to. Summer heat pushes hydration needs above your normal winter baseline. The research on hydration strategies during heat exposure recommends the most effective hydration strategies were those which individualised electrolyte fortified fluid volumes to match for sweat loss. Not just more water… water plus electrolytes for extended heat exposure. Sports drinks, coconut water, or electrolyte tablets. This isn't about being an athlete. It's about matching your fluid intake to the increased losses of summer.

Reduce session length, increase frequency. Rather than one long summer study session that grinds through heat impairment, break the same total time into shorter sessions spaced through the day. Multiple 30-minute sessions in cool morning and evening hours produce better learning than one 90-minute session that goes through heat degradation. The distributed approach works with the summer temperature curve.

Protect sleep aggressively. Hot nights degrade sleep, which compounds daytime cognitive impairment. During heat waves, doing whatever you can to maintain sleep quality is one of the highest-leverage moves you can make. Cooler bedroom (even if it means cooling only that specific room). Lighter bedding. Cold showers before bed. Fans directed at your body while sleeping. These aren't luxuries… they're protecting the specific biological process that makes tomorrow's learning possible.

Match task type to available conditions. In Persona 5, Joker doesn't try to fight boss enemies during weak states… he handles what fits current conditions and saves harder content for when his party's ready. Your summer studying works the same way. Complex new material during cool morning hours. Review and consolidation during afternoon heat. Reading familiar material during hot evening hours. The task-matching produces dramatically better outcomes than trying to do everything equally through all conditions.

Use pre-cooling strategically for specific hard tasks. If you have to do something cognitively demanding during a hot part of the day, deliberately pre-cool. Cold shower or cold water splash 30 minutes before the task. Sit in air conditioning for 15 minutes before. Cold drinks during the task. These are the specific interventions the research supports for maintaining cognitive performance under heat stress.

Accept lower daily output during heat waves. During genuinely extreme heat, your total daily learning output will be lower than during cooler weather. Trying to maintain winter output during summer heat produces exhaustion that doesn't sustain. Accept the reduction. Focus on quality of the sessions you can actually run rather than trying to force sessions that won't produce results.

Consider location strategy. If your home cooling isn't adequate, seeking cooler public spaces for demanding work is legitimate. Libraries, air-conditioned cafés, coworking spaces, malls, community centers. The cost of a coffee at a well-cooled café is often less than the productivity cost of trying to work in a too-hot home. This isn't giving up. It's matching environment to task.

Some patterns that most learners try and that don't work as well as they seem like they should.

Just pushing through with more coffee. Caffeine doesn't compensate for heat-induced cognitive impairment. It provides temporary alertness without addressing the underlying thermal load on your body. In severe heat, additional caffeine can actually increase your body's heat production, making the situation worse.

Cooling only during work sessions. The research shows pre-cooling is more effective than cooling during heat exposure. Trying to cool yourself while you're already too hot is less effective than cooling before you get too hot.

Waiting for the weather to cool down. For many climates, meaningful cooling doesn't happen until September or October. Waiting produces months of lost progress. The learners who work with summer heat produce dramatically more learning than the learners who wait for autumn.

Ignoring humidity. Cognitive performance research includes humidity as a factor. Hot and humid is worse than hot and dry at the same temperature. In humid climates, dehumidifiers can be as important as air conditioning for making study spaces workable.

Assuming you're adapting. Some heat acclimation happens naturally over a summer. But this adaptation is limited and doesn't eliminate the cognitive effects… it just moderates them somewhat. Don't assume you've adapted just because the heat feels less extreme after a few weeks.

Here's what I want you to take from all this. Summer heat produces measurable cognitive impairment that no amount of discipline fully compensates for. Trying to ignore this reality doesn't make you tougher… it makes you less productive. The learners who work with the reality of summer heat produce dramatically more learning during hot months than the learners who try to pretend the heat doesn't matter.

The playbook I've outlined isn't dramatic. Schedule demanding work for cool hours. Pre-cool before hard sessions. Hydrate more aggressively than you think you need. Protect sleep. Reduce session length. Match task type to conditions. Accept lower total output during genuinely extreme heat. Consider location strategy. These are all modest adjustments. Together they produce categorically better summer learning outcomes than pure discipline through impairment can achieve.

If you've been in the pattern of trying to push through summer heat with willpower and getting frustrated by your reduced output, please consider that the issue isn't your character. It's that heat is doing what heat does to human brains. The interventions that work aren't about being tougher. They're about being smarter about when and how you do the cognitive work you're trying to do.

The specific practical move I'd suggest: this week, identify your coolest 2-hour window each day. Reserve that window specifically for your most cognitively demanding learning work. Move review and easier tasks to hotter parts of the day. Notice how the shift affects your total learning output over two weeks. Most learners who make this simple adjustment discover that working with summer conditions produces more results than trying to grind through them.

In Naruto, Rock Lee's insane physical training happens at specific times and with specific recovery periods… not continuously in all conditions. He's not less disciplined for structuring his training around what his body can actually handle. He's smarter about it. Your summer learning is the same. The intelligent structuring isn't a compromise of discipline. It's how discipline actually produces results in conditions that would defeat pure willpower.

Keep learning (and keep cool),

Ray